Bottom Decile Research Articles

Reducing Imaging Utilization in Primary Care Through Implementation of a Peer Comparison Dashboard.

High clinical variation has been linked to decreased quality of care, increased costs, and decreased patient satisfaction. We present the implementation and analysis of a peer comparison intervention to reduce clinical variation within a large primary care network. Evaluate existing variation in radiology ordering within a primary care network and determine whether peer comparison feedback reduces variation or changes practice patterns. Radiology ordering data was analyzed to evaluate baseline variation in imaging rates. A utilization dashboard was shared monthly with providers for a year, and imaging rates pre- and post-intervention were retrospectively analyzed. Providers within the primary care network spanning 1,358,644 outpatient encounters and 159 providers over a 3-year period. The inclusion of radiology utilization data as part of a provider's monthly quality and productivity dashboards. This information allows providers to compare their practice patterns with those of their colleagues. We measured provider imaging rates, stratified by modality, as well as order variation over time. We observed significant variation in imaging rates among providers in the network, with the top decile ordering an average of 4.2 times more than the lowest decile in the two years prior to intervention. Provider experience and training were not significantly associated with imaging utilization. In the first year after sharing utilization data with providers, we saw a 17.3% decrease in median imaging rate (p < 0.001) and a 21.4% reduction in provider variation between top and bottom deciles. Median ordering rate for more costly cross-sectional imaging, including CT, MRI, and nuclear medicine studies, decreased by 30.4% (p < 0.001), 20.2% (p = 0.008), and 41.8% (p = 0.002), respectively. Peer comparison feedback can shape provider imaging behavior even in the absence of targets or financial incentives. Peer comparison is a low-touch, low-cost intervention for influencing provider ordering and may have applicability in other clinical areas.

Variability in cesarean delivery rates among individual labor and delivery nurses compared to physicians at three attribution time points.

To examine the variability in the cesarean delivery (CD) rates of individual labor and delivery nurses compared with physicians at three attribution time points. Medical record data from nine hospitals in Washington State from January 2016 through September 2018. Retrospective, observational cohort design using an aggregated database of birth records. Chart-abstracted clinical data from a subset of nulliparous, term, singleton, vertex births attributed at admission, labor management, and delivery to nurses and physicians. Two classification methods were used to categorize nurse- and physician-level CD rates at three attribution time points and the reliability of these methods compared. The sample included 12556 births, 319 nurses, and 126 physicians. Overall, variation in nurse-level CD rates did not differ significantly across the three attribution time points, and the extent of variation was similar to that observed in physicians. However, agreement between attribution time points varied between 35 percent and 65 percent when classifying individual nurses into the top and bottom deciles. The average reliability of nurse-level CD rates was 32 percent at admission (IQR 22.0 percent to 38.7 percent), 32.6 percent at labor (IQR 23.1 percent to 40.9 percent), and 29.3 percent (IQR 20.9 percent to 35.8 percent) at delivery. The average reliability of physician-level CD rates was higher: 54.2 percent (IQR 38.7 percent to 71.4 percent) at admission, 62.5 percent (IQR 49.0 percent to 79.6 percent) at labor management, and 66.1 percent (IQR 53.7 percent to 81.2 percent) at delivery. Feedback on nurse-level CD rates as part of routine clinical quality audits can provide insight into nurse performance in the context of other individual-level and unit-level information. To reliably distinguish individual nurse performance, larger sample sizes are needed.

The Influence of Health in Early Adulthood on Male Fertility

AbstractDespite the large literature examining predictors of fertility, previous research has not offered a population‐level perspective on how health in early adulthood is related to male fertility. Using Swedish population and military conscription registers, we study how body mass index (BMI), physical fitness, and height are associated with total fertility and parity transitions by 2012 among 405,427 Swedish men born 1965–1972, meaning we observe fertility up to age 40 or older. Applying linear regression and sibling fixed effects, we find that these anthropometric measures are strong predictors of fertility, even after accounting for education and cumulative income. Men with a “normal” BMI and in the highest decile of physical fitness have the most children. Men who were obese at ages 17–20 had a relative probability of childlessness almost twice as high as men who had a “normal” BMI, and men in the bottom decile of physical fitness had a relatively probability of childlessness more than 50 percent higher than men in the top decile. In sibling comparison models the tallest men have the most children and men in the lowest two deciles of height have significantly lower fertility. Further analyses show that the strong associations persist even among men who married.

The informalization of the Egyptian economy (1998–2012): a driver of growing wage inequality

ABSTRACT We run recentered influence function (RIF) regressions, using Firpo et al. (2007) distributional approach to identify each control variable’s contribution on the decomposition of wage changes. Using the Egyptian Labour Market Surveys 1998–2012 for waged men we find that wage changes between 1998 and 2012 mainly resulted in increased inequality. The richer percentiles have persistently enjoyed disproportionately larger positive changes in real hourly wages. Whilst increasing in all three wage gaps, inequality increased the most between the top and bottom deciles (90–10 gap), i.e. between the lowest and highest wage earners. This increase in inequality is primarily driven by the unexplained wage structure effect. The distinct labour market segments are foremost responsible for the increased inequality trend. Private sector informality is the largest contributor to increased inequality. The sector does not adhere to a minimum wage, and being unregulated it has responded dramatically to the severe competitive pressures caused by the departing middle classes of the public sector. It suppressed mid and low-end wages resulting in sharp wage gaps at the tails. Public sector wage setting dynamics and the direction of labour movements since liberalization cause the sector to contribute more to wage inequality than does its formal private counterpart.

The Acrosomal Status of Density Purified Spermatozoa Differentiates Men from Couples in IVF and ICSI Treatment and Is Associated with Fecundity.

The acrosome of the spermatozoa is required for fertilization and in the raw ejaculate the percentage of viable acrosome-intact spermatozoa, the acrosomal status, is higher among men with good semen quality. Here we investigated if the acrosomal status of the processed semen preparations used at a fertility clinic can also be informative and whether it is associated with fecundity. The acrosomal status was measured by image cytometry on purified semen samples from couples during in vitro fertilization (IVF) (n = 99) and intracytoplasmic sperm injection (ICSI) (n = 107) treatment. Purified frozen-thawed donor samples were also analyzed (n = 199). In purified semen preparations the acrosomal status was significantly higher among sperm donors (p = 5.3 × 10−8) and men from IVF couples (p = 2.2 × 10−5) when compared to men from ICSI couples. A significant difference was also found between female, male and mixed factor infertility (p = 0.003). No association with lifestyle factors was found. In frozen-thawed donor samples, a significant positive (r = 0.16, p = 0.025) association with the number of pregnancies per sold straw was observed together with an area under the curve of 75.3%, when comparing the top and bottom deciles. Our results indicate that the acrosomal status may be a valuable parameter for personalizing fertility treatments and might be a good predictor of pregnancy success among normozoospermic men.

Comparison of Health Outcomes Among High- and Low-Income Adults Aged 55 to 64 Years in the US vs England

Socioeconomic differences in life expectancy, health, and disability have been found in European countries as well as in the US. Identifying the extent and pattern of health disparities, both within and across the US and England, may be important for informing public health and public policy aimed at reducing these disparities. To compare the health of US adults aged 55 to 64 years with the health of their peers in England across the high and low ranges of income in each country. Using data from the Health and Retirement Study (HRS) and the English Longitudinal Study of Ageing (ELSA) for 2008-2016, a pooled cross-sectional analysis of comparably measured health outcomes, with adjustment for demographic characteristics and socioeconomic status, was conducted. The analysis sample included community-dwelling adults aged 55 to 64 years from the HRS and ELSA, resulting in 46 887 person-years of observations. Data analysis was conducted from September 17, 2019, to May 12, 2020. Residence in the US or England and yearly income. Sixteen health outcomes were compared, including 5 self-assessed outcomes, 3 directly measured outcomes, and 8 self-reported physician-diagnosed health conditions. This cross-sectional study included 12 879 individuals and 31 928 person-years from HRS (mean [SD] age, 59.2 [2.8] years; 51.9% women) and 5693 individuals and 14 959 person-years from ELSA (mean [SD] age, 59.3 [2.9] years; 51.0% women). After adjusting for individual-level demographic characteristics and socioeconomic status, a substantial health gap between lower-income and higher-income adults was found in both countries, but the health gap between the bottom 20% and the top 20% of the income distribution was significantly greater in the US than England on 13 of 16 measures. The adjusted US-England difference in the prevalence gap between the bottom 20% and the top 20% ranged from 3.6 percentage points (95% CI, 2.0-5.2 percentage points) in stroke to 9.7 percentage points (95% CI, 5.4-13.9 percentage points) for functional limitation. Among individuals in the lowest income group in each country, those in the US group vs the England group had significantly worse outcomes on many health measures (10 of 16 outcomes in the bottom income decile); the significant differences in adjusted prevalence of health problems in the US vs England for the bottom income decile ranged from 7.6% (95% CI, 6.0%-9.3%) vs 3.8% (95% CI, 2.6%-4.9%) for stroke to 75.7% (95% CI, 72.7%-78.8%) vs 59.5% (95% CI, 56.3%-62.7%) for functional limitation. Among individuals in the highest income group, those in the US group vs England group had worse outcomes on fewer health measures (4 of 16 outcomes in the top income decile); the significant differences in adjusted prevalence of health problems in the US vs England for the top income decile ranged from 36.9% (95% CI, 33.4%-40.4%) vs 30.0% (95% CI, 27.2%-32.7%) for hypertension to 35.4% (95% CI, 32.0%-38.7%) vs 22.5% (95% CI, 19.9%-25.1%) for arthritis. For most health outcomes examined in this cross-sectional study, the health gap between adults with low vs high income appeared to be larger in the US than in England, and the health disadvantages in the US compared with England are apparently more pronounced among individuals with low income. Public policy and public health interventions aimed at improving the health of adults with lower income should be a priority in the US.

Bailing out the Kids: New Evidence on Informal Insurance from one Billion Bank Transfers

We combine transaction-level data from the largest retail bank in Denmark and individual-level data from government registers to study informal insurance within social networks. Accounting for transfers in cash (money transfers) and in kind (cohabitation), we estimate that family and friends jointly replace around 7 cents of the marginal dollar lost within the bottom income decile, but much less at higher income levels. We document that informal insurance covers other adverse events than income losses: expenditure shocks, family ruptures and financial distress. Parents appear to be the key providers of informal insurance with a small amount of insurance coming from siblings and virtually none from grandparents and friends. Replacement rates vary monotonically with parent economic resources.

Genetic Risk Scores for Complex Disease Traits in Youth.

For most disease-related traits the magnitude of the contribution of genetic factors in adolescents remains unclear. Twenty continuous traits related to anthropometry, cardiovascular and renal function, metabolism, and inflammation were selected from the ongoing prospective Tracking Adolescents' Individual Lives Survey cohort in the Netherlands with measurements of up to 5 waves from age 11 to 22 years (n=1354, 47.6% males) and all traits available at the third wave (mean age [SD]=16.22 [0.66]). For each trait, unweighted and weighted genetic risk scores (GRSs) were generated based on significantly associated single nucleotide polymorphisms identified from literature. The variance explained by the GRSs in adolescents were estimated by linear regression after adjustment for covariates. Except for ALT (alanine transaminase), all GRSs were significantly associated with their traits. The trait variance explained by the GRSs was highest for lipoprotein[a] (39.59%) and varied between 0.09% (ALT) and 18.49% (LDL [low-density lipoprotein]) for the other traits. For most traits, the variances explained in adolescents were comparable with or slightly smaller than those in adults. Significant increases of trait levels (except ALT) and increased risks for overweight/obesity (odds ratio, 6.41 [95% CI, 2.95-15.56]) and hypertension (odds ratio, 2.86 [95% CI, 1.39-6.17]) were found in individuals in the top GRS decile compared with those at the bottom decile. Variances explained by adult-based GRSs for disease-related traits in adolescents, although still relatively modest, were comparable with or slightly smaller than in adults offering promise for improved risk prediction at early ages.

YAP1 positive small-cell lung cancer subtype is associated with the T-cell inflamed gene expression profile and confers good prognosis and long term survival.

9019 Background: The dominant expression of transcription factors ASCL1, NeuroD1, YAP1 or POU2F3 characteristically defines four small cell lung cancer (SCLC) subtypes (SCLC-A, SCLC-N, SCLC-Y and SCLC-P). The clinical validation and biological relevance of these emerging SCLC subtypes is currently lacking. Methods: Using the Illumina TruSeq RNA Exome Kit, we generated RNA-Seq data from 61 cases of SCLC and pulmonary carcinoid to interrogate gene expression differences in SCLC subtypes as well as in survival outliers (top and bottom decile) matched for clinically relevant prognostic factors and treatment. We also assessed YAP1 protein expression in a blinded fashion by immunohistochemistry in 130 SCLC cases. Results: We successfully classified 68% of SCLC into one of the four SCLC subtypes whereas 81.5% of carcinoids did not fit into any of these categories. GSEA for differentially expressed genes between outlier subgroups showed significant upregulation of interferon gamma and interferon alpha response genes in late survivors. Moreover, a previously validated 18-gene T-cell inflamed gene expression profile was upregulated in late survivors and in the SCLC-Y subtype. Furthermore, the SCLC-Y subtype and late survivors showed higher expression of HLA gene family and reduced expression of cancer testis antigens. The median (95%CI) OS was 14 (4.3, 28.8), 16.7 (0.9, NA), 8.1 (2, 9.7) and 20.1 (0.6, 39.5) months respectively, for SCLC-A, N, P and Y subtypes. YAP-1 protein expression was positive in 17 of 130 (13%) SCLC cases. The majority of cases with positive YAP1 expression by immunohistochemistry, 12 of 17 cases (70.6%), were limited stage SCLC at the time of original diagnosis. Conclusions: SCLC subtypes have clinical implication as predictive and prognostic biomarker. SCLC-Y subtype is enriched for T-cell inflamed phenotype and long term survival, and may predict for clinical benefit of immunotherapy.

Revisiting the gender wage gap in the United States

In this paper, we revisit the gender wage inequality in the United States with a focus on the deciles level wage-distribution in the USA during 1986 to 2016. We find that with the inclusion of part time employed men and women, the overall ratio of women’s to men’s wages in 1986 was 53 percent and this ratio increased to 67 percent as of 2016, suggesting a very moderate decline in overall gender wage gap over three decades. Moreover, our study decomposes the trends of the gender wage gap by the deciles and provides a description of the trends at the decile level for the recent years. We find that a higher gender unemployment gap has been associated with lower gender wage gap. Moreover, although the wage gap has declined moderately, within each gender, the wage-income share of the bottom decile to the top decile has dropped (and Coefficient of Variation has gone up), with a higher magnitude for women, suggesting an increase in wage inequality within each gender with a higher intensity for women. Finally, we demonstrate that traditional economic “reasons” for the gender wage gap–part time jobs and lack of skill–fail to explain the current gap convincingly, indicating an implicit gender discrimination.

Thyroid function in preterm infants and neurodevelopment at 2 years

ObjectivesPostnatal thyroid dysfunction is common in preterm infants but the relationship between mild dysfunction and neurodevelopment is unclear. Our aim is to describe the relationship between thyroid function and neurodevelopment.DesignCohort...

Multitrait analysis of glaucoma identifies new risk loci and enables polygenic prediction of disease susceptibility and progression.

Glaucoma, a disease characterized by progressive optic nerve degeneration, can be prevented through timely diagnosis and treatment. We characterize optic nerve photographs of 67,040 UK Biobank participants and use a multitrait genetic model to identify risk loci for glaucoma. A glaucoma polygenic risk score (PRS) enables effective risk stratification in unselected glaucoma cases and modifies penetrance of the MYOC variant encoding p.Gln368Ter, the most common glaucoma-associated myocilin variant. In the unselected glaucoma population, individuals in the top PRS decile reach an absolute risk for glaucoma 10 years earlier than the bottom decile and are at 15-fold increased risk of developing advanced glaucoma (top 10% versus remaining 90%, odds ratio = 4.20). The PRS predicts glaucoma progression in prospectively monitored, early manifest glaucoma cases (P = 0.004) and surgical intervention in advanced disease (P = 3.6 × 10-6). This glaucoma PRS will facilitate the development of a personalized approach for earlier treatment of high-risk individuals, with less intensive monitoring and treatment being possible for lower-risk groups.

Dynamics of Reallocation Within India’s Income Distribution

We investigate the nature and extent of reallocation occurring within the Indian income distribution, with a particular focus on the dynamics of the bottom of the distribution. We argue that income evolution is appropriately modeled using Geometric Brownian Motion (GBM). Specifically, we use the mechanism of GBM with a reallocation parameter that quantifies the extent and direction of reallocation in the distribution, as proposed by Berman et al. We find that since the early 2000s reallocation is negative, meaning that incomes are exponentially diverging and that there is a perverse redistribution of resources from the poor to the rich. It is well known that inequality has been rising in India in the recent past, but the assumption has been that while the rich benefit more than proportionally from economic growth, the poor are also better off than before. Our work refutes this as we find that India has moved from a regime of progressive to regressive redistribution, where continued impoverishment of the poor is directly spurring multiplicative income growth of the rich. Outcomes from the model suggest that income shares of the bottom decile (~1%) and bottom percentile (~0.03%) are at historic lows. We characterize these findings in the context of increasing in-formalization of the workforce in the formal manufacturing and service sectors, as well as the growing economic insecurity of the agricultural workforce in India. Significant structural changes will be required to address this phenomenon.

Fund Manager Skill in an Era of Globalization: Offshore Concentration and Mutual Fund Performance

We study how mutual fund managers gain an edge in selecting stocks in an era of globalization. We use textual analysis to construct a measure that captures a mutual fund’s offshore exposure concentration through holding US multinational firms. We find that funds with a higher offshore concentration index (OCI) perform significantly better, with the difference in four-factor alpha between the top and bottom deciles amounting to 2.95% per annum. Fund managers’ overweighting of firms with operations in certain countries can be partly attributed to their foreign ethnicity. High OCI fund managers have an information advantage regarding firms’ fundamentals, such as earnings.

Who Benefits from the Child Tax Credit?

The Child Tax Credit (CTC) provides a cash transfer of up to $2,000 per child under age 17 to millions of families in the United States. Using the Current Population Survey, we examine the aggregate effects and distributional implications of the rules governing children’s eligibility for the credit. While approximately 90% of all children qualify for at least a partial CTC, we document striking disparities in eligibility by income and race. The vast majority of children living in households in the bottom decile of the national AGI distribution are completely ineligible for the CTC and the majority of filers in the bottom thirty percent are eligible only for a partial credit. In contrast, virtually all children living in households in the top half of the income distribution qualify for the full credit amount. Approximately three-quarters of white and Asian children are eligible for the full CTC, compared to only about half of Black and Hispanic children. We use our results to estimate the distributional effects of a range of reforms to the CTC eligibility rules. Our results suggest that reforming the credit to include a larger share of children would more evenly distribute the credit’s benefits across children of different races and incomes. Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at www.nber.org.

Long Term Dynamics of Poverty Transitions in India

We use a stochastic model to explore dynamics of poverty in India between 1952-2006 and find that temporal transitions into and out of poverty are common. Model outcomes suggest that transitions out of poverty outnumber transitions into poverty in recent times, but that there is still a non-trivial proportion of individuals transitioning annually into poverty, highlighting the economic fragility of those near the poverty line. We also find a marked persistence of poverty over time, and although this has been slowly declining, a past in poverty still remains a good predictor of current poverty. Particularly concerning in this context are the income trajectories of those in the bottom decile of the income distribution, for whom escape from poverty appears infeasible given extant income dynamics. Finally, the dynamics suggest that transitional and persistent poverty are distinct phenomenon, and require distinct market and policy responses involving both missing markets and state action.

Impact of the Minimum Wage on Wages and Wage Inequality in 2019

The Object of the Study. Wages in Russiya and in its regionsThe Subject of the Study. Levels and differentiation of wages The Purpose of the Study is examining the impact of raising the minimum wage up to the subsistence minimum level of the able-bodied population in 2018-2019 on the dynamics of the main characteristics of wages at the federal and regional levels. The Main Propositions of the Article. The problem of spatial inequality includes socioeconomic inequality of the population which primarily depends on work remuneration as the main source of monetary income of households. The problems of work remuneration in the post-Soviet period are well-known – low levels, relatively high wage differentiation including cross-sectoral and cross-regional disparities. These were caused to a large extent by the low level of the minimum wage in the country. In May 2018 the minimum wage was raised up to the subsistence minimum level (poverty line) of the able-bodied population. Using the data from the wage surveys conducted by Rosstat in 2017 and 2019 the authors analyse the shifts in wage distribution of workers in Russiya and in its regions. The increase in the minimum wage resulted in a decline in the general differentiation of wages across the country and in the vast majority of regions, in reduction of the intra-industry and cross-regional differences. In 2019 the funds ratio (ratio of mean wages of the upper and the bottom deciles) exceeded 10 only in six regions, while in 2017 there were 29 such regions. In 2017 that ratio was below 8 only in 6 regions, in 2019 – in 45 regions, and in most of them (26) the average wage was 3 times below the subsistence minimum level of the able-bodied population. The analysis has shown that the low level of wages of most employees still remains an urgent problem, and reduction in wage inequality also has the reverse aspect. We know from the Soviet experience that low (as well as high) level of wage inequality does not promote work incentives and socioeconomic development of territories.

Effects of body mass index on relationship status, social contact and socio-economic position: Mendelian randomization and within-sibling study in UK Biobank.

BackgroundWe assessed whether body mass index (BMI) affects social and socio-economic outcomes.MethodsWe used Mendelian randomization (MR), non-linear MR and non-genetic and MR within-sibling analyses, to estimate relationships of BMI with six socio-economic and four social outcomes in 378 244 people of European ancestry in UK Biobank.ResultsIn MR of minimally related individuals, higher BMI was related to higher deprivation, lower income, fewer years of education, lower odds of degree-level education and skilled employment. Non-linear MR suggested both low (bottom decile, <22 kg/m2) and high (top seven deciles, >24.6 kg/m2) BMI, increased deprivation and reduced income. Non-genetic within-sibling analysis supported an effect of BMI on socio-economic position (SEP); precision in within-sibling MR was too low to draw inference about effects of BMI on SEP. There was some evidence of pleiotropy, with MR Egger suggesting limited effects of BMI on deprivation, although precision of these estimates is also low. Non-linear MR suggested that low BMI (bottom three deciles, <23.5 kg/m2) reduces the odds of cohabiting with a partner or spouse in men, whereas high BMI (top two deciles, >30.7 kg/m2) reduces the odds of cohabitation in women. Both non-genetic and MR within-sibling analyses supported this sex-specific effect of BMI on cohabitation. In men only, higher BMI was related to lower participation in leisure and social activities. There was little evidence that BMI affects visits from friends and family or having someone to confide in.ConclusionsBMI may affect social and socio-economic outcomes, with both high and low BMI being detrimental for SEP, although larger within-family MR studies may help to test the robustness of MR results in unrelated individuals. Triangulation of evidence across MR and within-family analyses supports evidence of a sex-specific effect of BMI on cohabitation.

Valuation and Long-Term Growth Expectations

A standard DCF corporate valuation usually includes a terminal value based on a long-term growth rate to reflect value from beyond the typical forecasting horizon of three to seven years. Despite often having a dominant effect on overall firm value, both the academic literature and practitioner conventions provide very little guidance on how this long-term growth rate should be determined. This paper addresses this gap: we undertake an exploratory analysis of how firms’ long-term growth is related to various firm and industry characteristics. We apply an extensive selection of potential predictors based on firm, industry, and market characteristics, in order to explain the variation in firms’ long-term growth rates. As such, we provide a predicted long-term growth rate for all firms, which can then be used as an input into a DCF valuation. We find that market prices do not seem to capture the full information that we find in long-term growth predictions. Thus, a trading strategy that goes long the decile with the highest long-term growth expectations and short the bottom decile yields positive and statistically significant abnormal returns in the range from ten to thirteen percent per year.

Role of maternal age at birth in child development among Indigenous and non-Indigenous Australian children in their first school year: a population-based cohort study

Indigenous Australian children are twice as likely to score poorly on developmental outcomes at age 5 years than their non-Indigenous peers. Indigenous children are also more likely to be born to younger mothers. We aimed to quantify the relationship between maternal age at childbirth and early childhood development outcomes in Indigenous and non-Indigenous children. In this population-based, retrospective cohort study, we used data from the Australian Early Development Census (AEDC) that were probabilistically linked by the New South Wales (NSW) Centre for Health Record Linkage to several NSW administrative datasets, including the Perinatal Data Collection, the Register of Births, Deaths and Marriages (for birth registrations), the Admitted Patient Data Collection, and public school enrolment records, as part of the Seeding Success study. The resulting data resource comprises a cohort of 166 278 children born in NSW whose first year of school was reported in a 2009 or 2012 AEDC record (which were the years of AEDC data available at the time of data linkage). The primary outcome was the aggregate outcome of developmental vulnerability (scores in the bottom decile, according to the 2009 benchmark, on one or more of the five AEDC domains, which include physical, social, emotional, language and cognitive, and communication development). This outcome was measured in singleton children without special needs recorded on the AEDC, in those with available developmental data. As a secondary outcome analysis, we also repeated the main analyses on the outcome of developmental vulnerability on the individual domains. We estimated the absolute risk of developmental vulnerability by maternal age in Indigenous and non-Indigenous populations, and we also estimated the risk difference and relative risk between Indigenous and non-Indigenous children by use of modified Poisson regression. Of 166 278 children in the cohort, 107 666 (64·8%) children were enrolled in a public school in NSW in 2009 or 2012, of whom 7994 (7·4%) children were Indigenous (ie, they, or either parent, were recorded as Aboriginal or Torres Strait Islander on one or more birth records) and 99 672 (92·6%) children were not Indigenous. After exclusions, the final study population included 99 530 children (7206 [7·2%] Indigenous and 92 324 [92·8%] non-Indigenous). Of those for whom developmental outcome data were available, 2581 (35·9%) of 7180 Indigenous children and 18 071 (19·7%) of 91 835 non-Indigenous children were developmentally vulnerable on one domain or more. The risk of developmental vulnerability decreased with maternal ages between 15 and 39 years, but the decrease in risk with maternal age was significantly steeper in non-Indigenous than Indigenous children. Developmental vulnerability is most common in Indigenous and non-Indigenous children born to young mothers; however, Indigenous children have an increased risk of this outcome across most of the maternal age range. Policies that improve the socioeconomic circumstances of Indigenous children and families could promote better developmental outcomes among Indigenous children. Culturally appropriate support for Indigenous children, including those born to young mothers and disadvantaged families, could also reduce early childhood developmental inequalities. The Australian National Health and Medical Research Council, Manitoba Centre for Health Policy.