Difference-in-differences Estimate Research Articles

International connectivity and the digital divide in Sub-Saharan Africa

In recent decades, international connectivity has improved significantly with the worldwide deployment of some 400 fiber submarine cables (SMCs), transmitting more than 99% of international telecommunications. If sub-Saharan African (SSA) has long remained excluded from this interconnection process, the maritime infrastructure network has recently densified and spurred an African connectivity catch-up. This paper estimates the impact of SMC deployment on the digital divide in a sample of 45 SSA countries covering the period of 1990–2014. Difference in differences (DID) estimations are conducted and highlight the particular contribution of SEACOM and EASSy cables, laid in 2009–2010, to Internet penetration in Eastern and Southern Africa. According to DID estimates, the rollout of these SMCs has yielded a 3–5 percentage point increase in Internet penetration rates in this region compared to the rest of SSA. This is a remarkable advancement, since this variation corresponds approximately to the level of Internet penetration in the subcontinent prior to their arrival.

Examining the economic effects of emissions trading scheme in China

This paper examined the economic impacts of China’s emissions trading system (ETS), implemented in 2013, in terms of gross domestic product (GDP) and per capita GDP. The methodology drew on a difference-in-differences (DID) method using dynamic panel data for 30 provincial regions. The estimation results show that implementing an ETS policy has statistically significant negative effects on economic growth. When considering the additional control variables, these effects are still statistically significant. Furthermore, these negative impacts increase over time with respect to both GDP and per capita GDP. The counterfactual tests confirm the robustness of our DID estimation results. The specific influence mechanism of China’s ETS policy was finally discussed. Our findings provide a quantitative decision-making support for popularizing ETS policy in China. Based on our DID model, empirical investigations of the ETS policy, especially concerning economic growth in other regions would produce prolific contributions to the literature.

Evaluation of US Hospital Episode Spending for Acute Inpatient Conditions After the Patient Protection and Affordable Care Act

Under the Patient Protection and Affordable Care Act (ACA), US hospitals were exposed to a number of reforms intended to reduce spending, many of which, beginning in 2012, targeted acute care hospitals and often focused on specific diagnoses (eg, acute myocardial infarction, heart failure, and pneumonia) for Medicare patients. Other provisions enacted in the ACA and under budget sequestration (beginning in 2013) mandated Medicare fee cuts. To evaluate the association between the enactment of ACA reforms and 30-day price-standardized hospital episode spending. This policy evaluation included index discharges between January 1, 2008, and August 31, 2015, from a national random 20% sample of Medicare beneficiaries. Data analysis was performed from February 1, 2019 to July 8, 2020. Payment reforms after passage of the ACA. 30-day price-standardized episode payments. Three alternative estimation approaches were used to evaluate the association between reforms following the ACA and episode spending: (1) a difference-in-difference (DID) analysis among acute care hospitals, comparing spending for diagnoses commonly targeted by ACA programs with nontargeted diagnoses; (2) a DID analysis comparing acute care hospitals and critical access hospitals (not exposed to reforms); and (3) a generalized synthetic control analysis, comparing acute care and critical access hospitals. Supplemental analysis examined the degree to which Medicare fee cuts contributed to spending reductions. A total of 7 634 242 index discharges (4 525 630 [59.2%] female patients; mean [SD] age, 79.31 [8.02] years) were included. All 3 approaches found that reforms following the ACA were associated with a significant reduction in episode spending. The DID estimate comparing targeted and untargeted diagnoses suggested that reforms following the ACA were associated with a -$431 (95% CI, -$492 to -$369; -2.87%) change in total spending, while the generalized synthetic control analysis suggested that reforms were associated with a -$1232 (95% CI, -$1488 to -$965; -10.12%) change in total episode spending, amounting in a total annual savings of $5.68 billion. Cuts to Medicare fees accounted for most of these savings. In this policy evaluation, the ACA was associated with large reductions in US hospital episode spending.

Association of Medicaid Expansion With Rates of Utilization of Cardiovascular Therapies Among Medicaid Beneficiaries Between 2011 and 2018.

The Affordable Care Act expanded Medicaid eligibility allowing low-income individuals greater access to health care. However, the uptake of state Medicaid expansion has been variable. It remains unclear how the Medicaid expansion was associated with the temporal trends in use of evidence-based cardiovascular drugs. We used the publicly available Medicaid Drug Utilization and Current Population Survey to extract filled prescription rates per 1000 Medicaid beneficiaries of statins, antihypertensives, P2Y12 inhibitors, and direct oral anticoagulants. We defined expander states as those who expanded Medicaid on or before January 1, 2014, and nonexpander states as those who had not expanded by December 31, 2018. Difference-in-differences (DID) analyses were performed to compare the association of the Medicaid expansion with per-capita cardiovascular drug prescription rates in expander versus nonexpander states. Between 2011 and 2018, the total number of prescriptions among all Medicaid beneficiaries increased, with gains of 89.7% in statins (11.0 to 20.8 million), 76% in antihypertensives (35.3 to 62.2 million), and 37% in P2Y12 inhibitors (1.7 to 2.3 million). Medicaid expansion was associated with significantly greater increases in quarterly prescriptions (per 1000 Medicaid beneficiaries) of statins (DID estimate [95% CI]: 22.5 [16.5-28.6], P<0.001), antihypertensives (DID estimate [95% CI]: 63.2 [47.3-79.1], P<0.001), and P2Y12 inhibitors (DID estimate [95% CI]: 1.7 [1.2-2.2], P<0.001). Between 2013 and 2018, >75% of the expander states had increases in prescription rates of both statins and antihypertensives. In contrast, 44% of nonexpander states saw declines in statins and antihypertensives. The Medicaid expansion was not associated with higher direct oral anticoagulants prescription rates (DID estimate [95% CI] 0.9 [-0.3 to 2.1], P=0.142). The 2014 Medicaid expansion was associated with a significant increase in per-capita utilization of cardiovascular prescription drugs among Medicaid beneficiaries. These gains in utilization may contribute to long-term cardiovascular benefits to lower-income and previously underinsured populations.

Associations of Early Medicaid Expansion and Cancer Mortality

There is a growing body of evidence that Medicaid expansion improves insurance rates and leads to earlier cancer diagnoses. However, there is no published data to date showing an improvement in survival or mortality for cancer patients. Our objective was to determine whether early Medicaid expansion (2010-2011) was associated with decreased cancer mortality rates. Mortality rates were obtained from the Surveillance, Epidemiology, and End Results (SEER) program in the year ranges available in SEER: 2005-2007 (pre-expansion) and 2012-2016 (post-expansion). Deaths in 2008-2011 were excluded as a phase-in/washout period. Difference-in-differences (DID) analyses were utilized to compare changes in mortality rates from pre- to post-expansion between early expansion (EXP states: CA, CT, DC, MN, NJ, and WA) and non-early expansion states (NEXP states: all others). Adjusted DID analyses were based on county-year group level observations and accounted for county-level covariates. Mortality rates were calculated for all malignancies combined, screenable cancers, and cancer sites with leading causes of death. To ensure minimal confounding due to differing mortality trends between EXP and NEXP states (i.e. to test the parallel trends assumption), changes in cancer mortality rates from 2002-2004 to 2005-2007 and from 2005-2007 to 2008-2011 were compared between EXP and NEXP states. There were 270,150 and 1,148,638 cancer deaths in EXP and NEXP states, respectively. Cancer mortality rates (rate = # deaths / 100,000 persons) declined in both EXP (rate = 75.7 pre-expansion to 64.7 post-expansion) and NEXP (rate = 88.0 to 77.9) states after early Medicaid expansion. In adjusted DID analyses, there was a reduction of 1.30 (95% CI = 0.62 to 1.99, P = .0001) cancer deaths/100,000 persons in EXP relative to NEXP states. Significant expansion-associated reductions were observed for liver and pancreas but not colon, breast, cervix, lung, or prostate cancers (Table). While there was a decrease in cancer mortality irrespective of expansion status, early Medicaid expansion was associated with a decrease of 1.3 cancer deaths per 100,000 persons, translating to about 900 cancer deaths prevented in early expansion states due to Medicaid expansion (based on 2013 EXP states population = 69.2M). As more data emerge, future studies should describe longer-term trends in mortality post-Medicaid expansion.Abstract 202; TableAdjusted DID estimates by cancer siteDID Estimate (95% CI)PAll Malignancies-1.30 (-1.99, -0.62)<0.001Breast0.21 (-0.24, 0.66)0.36Cervix-0.20 (-0.41, 0.02)0.076Colon0.06 (-0.14, 0.28)0.52Liver-0.23 (-0.39, -0.07)0.006Lung0.18 (-0.13, 0.50)0.25Pancreas-0.22 (-0.38, -0.05)0.012Prostate-0.18 (-0.39, 0.02)0.082 Open table in a new tab

The Role of Parallel Trends in Event Study Settings: An Application to Environmental Economics

Difference-in-differences (DID) research designs usually rely on variation of treatment timing such that, after making an appropriate parallel trends assumption, one can identify, estimate, and make inference about causal effects. In practice, however, different DID procedures rely on different parallel trends assumptions (PTAs), and recover different causal parameters. In this paper, we focus on staggered DID (also referred as event studies) and discuss the role played by the PTA in terms of identification and estimation of causal parameters. We document a “robustness” versus “efficiency” trade-off in terms of the strength of the underlying PTA and argue that practitioners should be explicit about these trade-offs whenever using DID procedures. We propose new DID estimators that reflect these trade-offs and derive their large sample properties. We illustrate the practical relevance of these results by assessing whether the transition from federal to state management of the Clean Water Act affects compliance rates.

Doubly robust difference-in-differences estimators

This article proposes doubly robust estimators for the average treatment effect on the treated (ATT) in difference-in-differences (DID) research designs. In contrast to alternative DID estimators, the proposed estimators are consistent if either (but not necessarily both) a propensity score or outcome regression working models are correctly specified. We also derive the semiparametric efficiency bound for the ATT in DID designs when either panel or repeated cross-section data are available, and show that our proposed estimators attain the semiparametric efficiency bound when the working models are correctly specified. Furthermore, we quantify the potential efficiency gains of having access to panel data instead of repeated cross-section data. Finally, by paying particular attention to the estimation method used to estimate the nuisance parameters, we show that one can sometimes construct doubly robust DID estimators for the ATT that are also doubly robust for inference. Simulation studies and an empirical application illustrate the desirable finite-sample performance of the proposed estimators. Open-source software for implementing the proposed policy evaluation tools is available.

144-LB: Medicaid Expansion and Utilization of Antihyperglycemic Therapies

Background: Certain antihyperglycemic therapies modify CV disease courses in DM, but their uptake in practice appears limited among low-income adults. Methods: We employed a difference-in-difference (DiD) design to study the association between Medicaid Expansion and non-insulin antihyperglycemic prescriptions. We used 2012-2017 National and State Medicaid data to compare prescription claims between states that did (n=25) and did not expand (n=26) Medicaid by Jan 2014. Results: Following Medicaid Expansion, average quarterly non-insulin antihyperglycemic therapies/1000 enrollees increased by 4% in expansion and 2% in non-expansion states (left panel) with modest variation (right panel). Use of SGLT2i and GLP-1RA grew faster in early expansion than non-expansion states. DiD estimates for prescription change after Medicaid Expansion between expansion vs. non-expansion states was 1.6 (1.00 to 2.20; P&amp;lt;0.001) for all non-insulin therapies, 0.11 (-0.02 to 0.25; P=0.10) for SGLT2i, and 0.11 (0.04 to 0.18; P=0.002) for GLP-1RA. Excluding 7 states that expanded Medicaid after Jan 2014 yielded similar results. Conclusion: Medicaid Expansion was associated with greater access to non-insulin antihyperglycemic therapies, including GLP-1RA, among newly insured low-income adults, even after accounting for more DM detection. Future studies are needed to understand if policies facilitating these therapeutic changes impact CV health. Disclosure A. Sumarsono: None. L. Buckley: None. S.R. Machado: None. R.K. Wadhera: None. H. Warraich: None. R.J. Desai: Research Support; Self; Bayer AG, Novartis AG. B.M. Everett: Consultant; Self; Amarin Corporation, Amgen, Merck &amp; Co., Inc., National Institute of Diabetes and Digestive and Kidney Diseases, Roche Diagnostic USA. Consultant; Spouse/Partner; Sequana. Consultant; Self; U.S. Food and Drug Administration. Research Support; Self; National Heart, Lung, and Blood Institute. D.K. McGuire: Consultant; Self; Afimmune, Applied Therapeutics, Merck Sharp &amp; Dohme Corp., Metavant. Other Relationship; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Eisai Co., Ltd., Eli Lilly and Company, Esperion Therapeutics, Inc., GlaxoSmithKline plc., Janssen Pharmaceuticals, Inc., Lexicon Pharmaceuticals, Inc., Merck &amp; Co., Inc., Novo Nordisk A/S, Pfizer Inc., Sanofi-Aventis. G.C. Fonarow: Consultant; Self; Abbott, AstraZeneca, Janssen Pharmaceuticals, Inc., Medtronic, Novartis Pharmaceuticals Corporation. J. Butler: Consultant; Self; Amgen, Array BioPharma, AstraZeneca, Bayer AG, Boehringer Ingelheim Pharmaceuticals, Inc., Bristol-Myers Squibb, CVRx, G3 Pharmaceuticals, Innolife Co., Ltd., Janssen Pharmaceuticals, Inc., Luitpold Pharmaceuticals, Inc., Medtronic, Merck &amp; Co., Inc., Novartis Pharmaceuticals Corporation, Relypsa, Inc., VIfor. A. Pandey: None. M. Vaduganathan: Advisory Panel; Self; Bayer AG, Boehringer Ingelheim Pharmaceuticals, Inc., Relypsa, Inc. Consultant; Self; Amgen, AstraZeneca, Baxter.

The effect of health education on knowledge and behavior toward respiratory infectious diseases among students in Gansu, China: a quasi-natural experiment

BackgroundThe respiratory infectious diseases (RID) threaten the health and life quality of school students. However, previous related studies were insufficient in research design and method applied. This study aimed to evaluate the effect of health education on the knowledge and behavior of students toward RID through difference-in-difference (DID) analysis in Gansu, China.MethodsIn 2015–2016, a one-year health education program in Gansu, China was conducted. The intervention group contained 1064 students before and 1001 students after the health education (2015 and 2016, respectively). The control group contained 1018 and 1001 students, respectively. The health education, including playing promotional cartoons, developing lectures, giving out handbook copies and making hand copy and blackboard newspapers, and publicity columns on RID, were conducted monthly from 2015 to 2016 in intervention group. The data were collected before and after the health education program with a questionnaire on the students’ knowledge and preventive behaviors regarding RID. The ×2 and t tests were performed to compare the accuracy rate and scores for RID knowledge and behavior of the two groups. DID estimation was conducted to evaluate the effect of health education on RID knowledge and behavior while controlling the non- equilibrium variables.ResultsAfter the health education program, the accuracy rate and scores of most items in the intervention group were significantly higher than those in the control group (P < 0.05) except for item k9 “What methods can prevent flu?”. The DID results wherein the demographics- age, nationality, and household register were controlled showed that health education significantly improved the accuracy rate of RID knowledge by 5.2–63.9% for most items, although the accuracy rates of items k2 “What’s the transmission way of the mumps?” and k9 were significantly decreased by 36.8 and 12.0%. The health education significantly improved the score of knowledge by 155.2% (P < 0.001) and the accuracy rate of all items of RID behavior by 2.9–51.5% except for item b3 “If you have phlegm, how do you usually deal with it?”. In addition, the health education also significantly improved the score of behavior toward RID of the sampled students by 138.2% (P < 0.001).ConclusionThe results of this study show that health education seemed to increase the RID knowledge and behavior of students. It is recommended that the health education should be enhanced and popularized in schools of China, and RID transmission routes and prevention methods should attract more attention.

Do employer-sponsored health insurance schemes affect the utilisation of medically trained providers and out-of-pocket payments among ready-made garment workers? A case–control study in Bangladesh

ObjectiveWe estimated the effect of an employer-sponsored health insurance (ESHI) scheme on healthcare utilisation of medically trained providers and reduction of out-of-pocket (OOP) expenditure among ready-made garment (RMG) workers.DesignWe used...

Liberalizing Art. Evidence on the Impressionists at the End of the Paris Salon

We analyze the Paris art market between the government-controlled Salon as a centralized organization of art exhibition and the system liberalized by the Republican government based on competition between independent exhibitions. The jury of the old Salon decided on submissions with a bias toward conservative art of the academic insiders, reducing demand for the outsiders, as confirmed by the impact on prices of the acceptance of Impressionists. With a difference-in difference estimation we provide evidence that the end of the government-controlled Salon in 1880 started the increase of the prices of the Impressionists relative to the insiders.

Liberalizing art. Evidence on the Impressionists at the end of the Paris Salon

We analyze the art market in Paris between the government-controlled Salon and the post-1880 system, when the Republican government liberalized art exhibitions. The jury of the old Salon decided on submissions with a bias in favor of conservative art of the academic insiders, erecting entry barriers against outsiders as the Impressionists. With a difference-in difference estimation, we provide evidence that the end of the government-controlled Salon contributed to start the price increase of the Impressionists relative to the insiders.

Opioid Prescription Rates and Asset Prices — Assessment of Causal Effects

We explore the link between county-level opioid prescription rates and asset prices, specifically, stock returns of firms headquartered in that county, as well as real estate prices. In order to establish the causal effects of opioid prescription rates on firm stock returns, we first apply an instrumental variable (IV) regression approach and use the number of clandestine drug laboratories in a county to be the instrumental variable. The results provide robust evidence that county-level opioid prescription rates have a negative causal effect on the equity returns of firms headquartered in that county. Furthermore, we analyze the effect of Medical Board of California's 2014 regulatory revision aimed at reducing controlled substance overdose due to prescriptions and implement a difference-in-differences (DiD) estimation. The DiD estimation results show that this policy change has a positive dynamic effect on Californian firms' equity returns. We also find that the opioid prescription reduction assistance program provided by California Health Care Foundation (CHCF) to certain counties in California helps to raise the median prices of existing single-family homes in those counties by $28,678 on average.

Impacts of community policing on security: evidence from Mbujimayi in the Democratic Republic of Congo

ABSTRACT This study adopts a quasi-experimental design to estimate the impact on security of the introduction of community policing in a district of the city of Mbujimayi, Democratic Republic of Congo. The authors suggest that security is best captured by a multidimensional index from which they derive a series of outcome indicators such as the incidence of insecurity, the vulnerability to insecurity, or the severity of insecurity. The data originate from representative surveys conducted at pre- and post-treatment times in the pilot and control districts. The main impact estimates are calculated using the Difference-in-Difference (DiD) approach. The DiD estimates are cross-checked with DiD estimates obtained with propensity score matched data to control for the selection bias inherent to quasi-experimental designs. After a year of treatment, the short-term effect of community policing is found to be efficient based on the security indicators and consistently so across approaches. The study finds that community policing impacted strongly on the two dimensions of security: access to policing services and police legitimacy. The effect of community policing is found however to be significantly higher for men than for women and to have had no or only marginal impact on younger women who remained vulnerable to insecurity even after treatment.

Employment Effects of Job Counseling for Disability Insurance Recipients

Many countries implement policies to promote labor market inclusion of disability support recipients. It is unclear whether such measures work. We exploit a quasi-experimental setting in Australia where compulsory job counseling was introduced in 2012 affecting only those social security disability insurance (DI) recipients below age 35. Using longitudinal administrative data on all DI recipients and applying a difference-in difference estimator, we find that the policy was largely ineffective and neither improved employment nor earnings.

Reducing Child Undernutrition through Dietary Diversification, Reduced Aflatoxin Exposure, and Improved Hygiene Practices: The Immediate Impacts in Central Tanzania

ABSTRACT The study aimed to quantify the immediate effects of dietary diversification, food safety, and hygiene interventions on child undernutrition in four rural villages in Kongwa district of central Tanzania. One hundred mothers with their children of less than 24 months old were recruited for this study. The difference-in-difference (DID) method was used to assess the effects of intensive intervention through a learning-by-doing process on the topic of aflatoxin free diversified food utilization and improved hygiene practices. Periodic anthropometric measurements were conducted on the 0th, 7th, 14th, and 21st days, and DID estimator showed the significant and positive average marginal effects of the intervention on Z-Scores being 0.459, 0.252, and 0.493 for wasting, stunting, and underweight, respectively. Notably, at the end of the study, the mean aflatoxin M1 level in urine samples decreased by 64% in the intervention group, while it decreased by 11% in the control group. The study provides quantitative evidence on intensive 21-day training for mothers incorporating integrated technologies yielded positive impacts on their children’s nutritional outcomes.

Global Air Network and Cross-border Venture Capital Mobility

Using 23-year panel data of cross-border venture capital investment and global air network expansion as a natural experiment, this paper investigates the effect of air travel on cross-border capital mobility. We find international airlines have a significant facilitating effect on venture capital mobility. Based on the difference-indifferences estimate, for our research period one additional flight per day leads to an increase in VC investment between the city pair by 0.14 deals on average per year (1.08 times the mean value). The heterogeneous analys indicates that, with more air connections, emerging industries and firms in earlier developmental stages receive more investment, and non-syndication investment increases more than syndication investment. In addition, we find the effect significantly increases with geographical distance: city pairs that are far away from each other experience a larger increase in VC flow after flight connections exist. Lastly, the evidence suggests that most of this increase in capital flows happens in wealthier cities. Connections between poor cities show little effect on VC flow. The paper presents evidence on the role of the global air network in reducing information transmission cost and raising the expectation for future growth potential. All results are shown to be robust using alternative VC investment measures and the regression discontinuity method.

2050. Effect of a Stewardship Intervention on Post-Prescriptive Antibiotic Timeouts in Nursing Homes

BackgroundAntibiotic overuse and misuse is a common problem in nursing homes (NHs). Meaningful improvements in the quality of antibiotic prescribing in NHs may be improved through post-prescriptive interventions (antibiotic timeouts) focused on stopping, streamlining and/or shortening ongoing antibiotic treatments. A recently completed trial of a complex antibiotic stewardship intervention provided us with an opportunity to explore to what extent NH providers engaged in antibiotic timeouts at baseline and the effects of the intervention on these behaviors.MethodsData on antibiotic prescriptions in 11 NHs (6 intervention, 5 control) were collected for 12 months prior and 13 months after intervention introduction. We categorized antibiotic change events (ACEs) as: (1) changes in dose, frequency, or route for the same antibiotic, (2) change to another antibiotic with different spectrum, and (3) early discontinuation (stopped after 2 days or less). Modifications considered to be routine (e.g., Azithromycin dose reduction from 500 to 250 mg) were not considered a meaningful ACE. Frequency of ACEs both overall and by type were compared using a difference in difference (DID) approach.ResultsOf 2647 NH initiated antibiotic events, 376 (14.2%) were modified over the study period. The most common type of modification was a change in spectrum (n = 241, 64.1%) followed by early discontinuation of the antibiotic (n = 118, 31.4%). The difference in ACEs before and after the intervention as well as DID estimates are detailed in the Table.ConclusionThe antibiotic stewardship intervention did not impact total ACEs but did appear to increase the frequency of discontinuation ACEs. An inability to capture data on shortening ACEs (e.g., reducing a treatment course from 14 to 7 days) was a limitation of this study. Additional research on how to foster more frequent and effective antibiotic timeouts in NHs is needed. Disclosures All authors: No reported disclosures.

Evaluating the Effect of Medicaid Expansion on Black/White Breast Cancer Mortality Disparities: A Difference-in-Difference Analysis

PURPOSE This analysis used a difference-in-difference (DID) fixed effects regression model to evaluate the impact of Medicaid Expansion on the disparity between black and white breast cancer mortality rates. Medicaid Expansion was designed to increase access to health care. Evidence is mixed, but theory and empirical data suggest that lower cost of care, through greater access to insurance, increases health care utilization and possibly improves the health of poor and sick populations. The goal of Medicaid Expansion was to improve equity. However, this major health policy has yet to be thoroughly investigated for its effect on health disparities. Many widely accepted methods exist to evaluate variations in health policy, but few studies have used such quasi-experimental designs to explore health disparities. The current study is motivated by one of today’s most stark inequalities: the disparity in breast cancer mortality rates between black and white women. To test the impact Medicaid Expansion had on the black/white breast cancer mortality ratio, a DID analysis calculated the policy’s average treatment effect (ATE). METHODS State-level breast cancer mortality data were obtained from the Centers for Disease Control and Prevention. Each state’s Medicaid Expansion status was provided by a Kaiser Family Foundation white paper. Two tests were conducted: one compared all expanding states with all nonexpanding states, and the other compared all expanding states with nonexpanding states that voted to expand (but did not by 2014). Fixed-effects and random-effects regression models were constructed for each specific age group. A Hausman test was calculated to determine which model was most appropriate. The DID regression models considered the year 2014 a wash-out period and compared 2012 and 2013 (pretreatment) to 2015 and 2016 (post-treatment). A graph was presented to test the necessary parallel trend assumption for expanding and nonexpanding states. DID estimators (average treatment effect) and respective P values were reported for each age group. Non–Medicaid-eligible age groups were included as a pseudo-control. RESULTS Medicaid Expansion did not lower the disparity in breast cancer mortality. Converse to expectations, the black/white mortality ratio increased in states expanding Medicaid for all Medicaid-eligible age groups, with significant effects in younger age groups ( P = .01 to .15). CONCLUSION Investigators should use proven quasi-experimental methods to analyze the effect of policy variation on health disparities. Policy makers must consider institutional factors that may limit minority groups from benefiting from macrochanges in health policy. These results suggest that states cannot solely rely on access to insurance to alleviate disparities in cancer or other chronic conditions. More exploration into the impacts of low-quality health systems remain warranted.

Lean manufacturing and productivity changes: the moderating role of R&D

PurposeThe purpose of this paper is to empirically investigate the effect of lean manufacturing on productivity changes and to identify the root sources of productivity changes. Furthermore, the authors explore the moderating effects of research and development (R&D) to examine the relationship between lean manufacturing and productivity changes.Design/methodology/approachThis paper employs the propensity score matching (PSM) model combined with the difference-in-difference (DID) estimation to overcome the selectivity bias. The Malmquist productivity index is used to capture productivity changes. By analyzing 671 Chinese manufacturing listed firms from 2009 to 2014, the moderating effects of R&D on the relationship between lean manufacturing and productivity changes are measured.FindingsThe results reveal that lean manufacturing implementation has non-significant effects on productivity changes in principle, while a detailed analysis indicates that lean manufacturing could improve scale efficiency significantly. While engaged in R&D could significantly improve the efficiency of technological changes for lean manufacturing implementation firms, there exist negative effects on pure technical efficiency.Research limitations/implicationsThis research only covers manufacturing listed firms in China. Further studies should extend the generalizability of the findings.Practical implicationsThis study helps managers to identify the important role of R&D on the relationship between lean manufacturing and productivity changes and provides insights into how to improve the lean manufacturing performance.Originality/valueThis paper appears to be one of the earliest studies on the relationship between lean manufacturing and productivity changes by applying the PSM combined with DID estimation in Chinese manufacturing environment.