Idiosyncratic Variation Research Articles

Peer gender composition and non-cognitive factors

ABSTRACT This note studies the relationship between the gender composition of a student’s peers and two of their non-cognitive factors: sense of belonging and self-worth. Using data from Add Health and exploiting idiosyncratic variation in the share of female peers across grades within schools, I find positive but small effects of a higher share of female peers for male students. I do not find statistically significant effects for female students, but I can rule out large positive effects.

Voting with one’s neighbors: Evidence from migration within Mexico

We study how proximate neighbors affect one’s propensity to vote using data on 12 million registered voters in Mexico. To identify this effect, we exploit idiosyncratic variation at the neighborhood block level resulting from approximately one million relocation decisions. We find that when individuals move to blocks where people vote more (less) they themselves start voting more (less). We show that this finding is not the result of selection into neighborhoods or of place-based factors that determine turnout, but rather peer effects. Consistent with this claim, we find a contagion effect for non-movers and show that neighbors from the same block are much more likely to perform an electoral procedure on the same exact day as neighbors who live on different blocks within a neighborhood.

Long-term labor market returns to upper secondary school track choice: Leveraging idiosyncratic variation in peers’ choices

Vocational education and training (VET) is theorized to play a dual role for inequality of labor market outcomes: the role of a safety net and the role of socioeconomic diversion. In this paper, we test these hypotheses by examining the long-term labor market returns to track choice in upper secondary education in Denmark using an instrumental variable approach that relies on random variation in school peers’ educational decisions. We report two main findings. First, VET diverts students on the margin to the academic track away from higher-status but not higher-paying occupations. Second, VET protects students on the margin to leaving school from risks of non-employment and unskilled work, also leading to higher earnings. These results suggest that in countries with a highly compressed wage structure, a strong VET system benefits students unlikely to continue to college, while causing few adverse consequences for students on the margin to choosing academic education.

Are girls always good for boys? Short and long term effects of school peers’ gender

This paper exploits idiosyncratic variations in school cohorts’ gender composition to investigate the short and long-term effects of school peers’ gender. Using French administrative data over the 2008–2012 period, it shows that the proportion of female peers’ in middle school not only affects students’ contemporaneous performance but also influences their subsequent educational attainment. More specifically, a larger share of girls among school peers increases girls’ test scores, reduces their dropout rates and increases their probability to graduate from high school several years later, especially in the scientific track. By contrast, it increases boys’ probability to attend a vocational school and decreases their high school graduation rate. I find suggestive evidence that these effects partially operate through a negative effect of opposite-gender peers on students’ school behaviour and through an adjustment of teacher behaviour based on the gender composition of the classroom.

The impact of adopting stress-tolerant maize on maize yield, maize income, and food security in Tanzania.

Productivity growth emanating from scientific advances offered by biotechnology and other plant breeding initiatives offers great promise for meeting the growing food demand worldwide. This justifies investments in agricultural research and development that have led to the development of stress‐tolerant maize varieties (STMVs) in Africa. While most literature has documented the average impacts of STMVs on productivity, this paper is premised on the fact that benefits from technology adoption are not the same across household. The paper addresses this information gap by examining potential heterogeneity in yield, income, and food security benefits from of adopting STMVs using a sample of 720 maize‐producing households from Tanzania. The dose‐response continuous treatment effect method supported by an endogenous switching probit model was used to estimate the heterogenous impact of STMV adoption on the three outcomes of interest. Results show that, overall, the adoption of stress‐tolerant maize varieties increased maize grain yield by about 1 ton/ha, maize income by about $62/ha. The adoption of STMVs also reduced the propensity to report mild, moderate, and severe food insecurity by 34%, 17%, and 6%, respectively. There are substantial idiosyncratic variations in the productivity, income, and food security effects depending on the scale of adoption, with a higher impact at lower dose levels of adoption. The heterogenous and pro‐poor nature of STMV adoption is also revealed through nonparametric results showing higher productivity benefits among households that are less endowed with wealth and knowledge. These findings underscore the need for further scaling of stress‐tolerant maize varieties for greater impact on the livelihoods of poor small‐scale farmers in Tanzania.

The Importance of Peer Quality for Completion of Higher Education

Using detailed Danish administrative data covering the entire population of students entering higher education in the period 1985 to 2010, we investigate the importance of a student’s peers in higher education for the decision to drop out. We use high school GPA as a predetermined measure of student ability and idiosyncratic variation in peer composition across cohorts within the same education and institution. Our findings suggest that peer ability is an important determinant of students’ drop out decisions as well as later labor market outcomes. Overall, we find that a one standard deviation increase in peers’ high school GPA reduces the probability of dropping out by 4.6 percentage points. This number masks considerable heterogeneity by level and field of study. Allowing for a more flexible specification, we find that low quality peers have adverse effects on the probability of dropping out while high quality peers have beneficial effects. These effects are more pronounced for lower ability students.

Innovations and earnings non‐synchronicity: evidence from industry M&A activities

AbstractThis paper investigates how earnings non‐synchronicity impacts associated with firm‐level research and development (R&D) investment vary as a function of industry‐level mergers and acquisitions (M&A) intensity. Investing in R&D enables firms to differentiate and gain competitive advantages; differentiation strategies increase idiosyncratic variation in firms’ earnings. We introduce an industry‐level contextual variable, industry‐level M&A, to capture variations in innovation novelty. We show that the positive relationship between R&D investment and earnings non‐synchronicity is increasing in the intensity of inside‐industry M&A but not outside‐industry M&A. This is consistent with our conjecture that M&A within an industry facilitate knowledge base expansion and induce more innovative R&D through complementary effects.

Idiosyncratic variation in the fitness costs of tetracycline-resistance mutations in Escherichia coli.

A bacterium's fitness relative to its competitors, both in the presence and absence of antibiotics, plays a key role in its ecological success and clinical impact. In this study, we examine whether tetracycline-resistant mutants are less fit in the absence of the drug than their sensitive parents, and whether the fitness cost of resistance is constant or variable across independently derived lines. Tetracycline-resistant lines suffered, on average, a reduction in fitness of almost 8%. There was substantial among-line variation in the fitness cost. This variation was not associated with the level of resistance conferred by the mutations, nor did it vary significantly across several genetic backgrounds. The two resistant lines with the most extreme fitness costs involved functionally unrelated mutations on different genetic backgrounds. However, there was also significant variation in the fitness costs for mutations affecting the same pathway and even different alleles of the same gene. Our findings demonstrate that the fitness costs of antibiotic resistance do not always correlate with the phenotypic level of resistance or the underlying genetic changes. Instead, these costs reflect the idiosyncratic effects of particular resistance mutations and the genetic backgrounds in which they occur.

Intrinsic Laryngeal Muscle Activity During Subvocalization

Subvocalization, the low-grade activity of speech articulator muscles while thinking or reading, may mediate phonological representations of verbal material. However, no literature exists that directly measures whether intrinsic laryngeal muscles (ILMs) are active during subvocalization. The possibility of ILM activation during subvocalization has implications for establishing appropriate baselines when experimental conditions involve linguistic features. In two separate studies, forty-five cisgender women completed one or two silentsil tasks (two in the first study, Experiments 1a and 1b, and one in the second, Experiment 2). Fine wire electromyography was used to directly measure ILM activity during an at-rest baseline and silent tasks used to determine whether subvocalization occurred (referred to hereafter as "subvocalization tasks"). Other muscles were measured via surface electromyography: submental muscle in Experiments 1a and 1b, anterior tibialis in Experiment 2, and upper trapezius in all experiments. Interrupted time-series analysis was used to directly measure changes in ILM activity from baseline to the subvocalization tasks. A paired two tailed t-test was used to measure mean differences in ILM activity across conditions for each participant. Some individuals displayed statistically significant increases from baseline during subvocalization tasks, whereas others displayed decreases. Cohen's d was used to calculate the effect size for each muscle across the three subvocalization conditions. Of the 21 muscles measured across three experiments, five yielded a small mean effect size, and the effect sizes for the remaining 16 muscles were negligible. At a group level, only the right cricothyroid showed statistically significant changes (Experiment 1b). The ILM responses during subvocalization vary in both magnitude and direction. Most but not all changes can be described as negligible. For future studies of ILM activity during conditions that involve linguistic processing, investigators should consider the idiosyncratic variation during subvocalization when determining the most appropriate baseline task.

Promoting student achievement in high school using school funding: evidence from quantile regression discontinuity design

Even though there are many quasi-experimental research in recent literature, there is still no consensus on whether an increase in school funding improves student achievement. Leveraging a natural experiment in South Korea, this study exploits the discontinuity in school funding rules to identify the impact of increased funding on the test scores of high-school students in a national assessment exam. The setting provides a useful context to study the effect of school funding because students typically attend largely similar schools that follow a standardized curriculum, thus eliminating the possibility of the results being contaminated by idiosyncratic variation in school-level characteristics. This study reports mean regression discontinuity estimates as well as quantile regression discontinuity estimates using a procedure suggested by Frandsen et al. (J Econom 168:382–395, 2012). The findings reveal that an increase in school funding, which is equal to approximately 300,000 won per student, results in improved exam performance, particularly in mathematics. Contrary to the stated purpose of the program, however, the evidence suggests that students in the middle and top of the ability distribution gained the most from the intervention, rather than students who are at the highest risk of failing.

Idiosyncratic Variations within the Metadiscursive Matrix of Modern Public Verbal Interaction

In order to be distinguished from the conventional verbal interactional context deliberate violations of the metadiscursive matrix are employed: 1) the informal register instead of the formal; 2) gradable adjectives and superlatives violate the expectation of objectivity and accuracy; 3) the self-conscious pragmatic-rhetoric strategies; 4) ample use of vulgarisms and offensive addresses; 5) a diversity of rhetoric means. These idiosyncratic variations function as the strategy of identification with the audience, and the effects achieved are as follows: 1) gaining attention; 2) distinguishing oneself from the context of similar speakers; 3) gaining and demonstrating power; 4) suspense; 5) convincing and persuasion for taking action.

The Importance of Peer Quality for Completion of Higher Education

Using detailed Danish administrative data covering the entire population of students entering higher education in the period 1985 to 2010, we investigate the importance of a student's peers in higher education for the decision to drop out. We use high school GPA as a predetermined measure of student ability and idiosyncratic variation in peer composition across cohorts within the same education and institution. Our findings suggest that peer ability is an important determinant of students' drop out decisions as well as later labor market outcomes. Overall, we find that a one standard deviation increase in peers' high school GPA reduces the probability of dropping out by 4.6 percentage points. This number masks considerable heterogeneity by level and field of study. Allowing for a more flexible specification, we find that low quality peers have adverse effects on the probability of dropping out while high quality peers have beneficial effects. These effects are more pronounced for lower ability students.

A value-at-risk approach to mis-estimation risk

Abstract Parametric mortality models permit detailed analysis of risk factors for actuarial work. However, finite data volumes lead to uncertainty over parameter estimates, which in turn gives rise to mis-estimation risk of financial liabilities. Mis-estimation risk can be assessed on a run-off basis by valuing the liabilities with alternative parameter vectors consistent with the covariance matrix. This run-off approach is especially suitable for tasks like pricing portfolio transactions, such as bulk annuities, longevity swaps or reinsurance treaties. However, a run-off approach does not fully meet the requirements of regulatory regimes that view capital requirements through the prism of a finite horizon, such as Solvency II’s one-year approach. This paper presents a methodology for viewing mis-estimation risk over a fixed time frame, and results are given for a specimen portfolio. As expected, we find that time-limited mis-estimation capital requirements increase as the horizon is lengthened or the discount rate is reduced. However, we find that much of the so-called mis-estimation risk in a one-year value-at-risk assessment can actually be driven by idiosyncratic variation, rather than parameter uncertainty. This counter-intuitive result stems from trying to view a long-term risk through a short-term window. As a result, value-at-risk mis-estimation reserves are strongly correlated with idiosyncratic risk. We also find that parsimonious models tend to produce lower mis-estimation risk than less-parsimonious ones.

Cross-sectional Variation of Option Implied Volatility Skew

The slope of the option implied volatility plot against the strike reflects the risk-neutral skewness of the underlying security's conditional return distribution. We identify two principal risk sources that contribute to the cross-sectional variation of individual stock options' implied volatility skew: the market risk exposure of the stock's return and the company's default risk. Once controlled for these two risk exposures and the implied volatility level, the remaining idiosyncratic variation of the implied volatility skew reflects more of investor expectation and sentiment on the stock's future price movement and can be used to predict future stock returns with more accuracy.

Voting with One's Neighbors: Evidence from Migration within Mexico

We study how proximate neighbors affect one’s propensity to vote using data on 12 million registered voters in Mexico. To identify this effect, we exploit idiosyncratic variation at the neighborhood block level resulting from approximately one million relocation decisions. We find that when individuals move to blocks where people vote more (less) they themselves start voting more (less). We show that this finding is not the result of selection into neighborhoods or of place-based factors that determine turnout, but rather peer effects. Consistent with this claim, we find a contagion effect for non-movers and show that neighbors from the same block are much more likely to perform an electoral procedure on the same exact day as neighbors who live on different blocks within a neighborhood.

Life cycle patterns of cognitive performance over the long run

Little is known about how the age pattern in individual performance in cognitively demanding tasks changed over the past century. The main difficulty for measuring such life cycle performance patterns and their dynamics over time is related to the construction of a reliable measure that is comparable across individuals and over time and not affected by changes in technology or other environmental factors. This study presents evidence for the dynamics of life cycle patterns of cognitive performance over the past 125 y based on an analysis of data from professional chess tournaments. Individual move-by-move performance in more than 24,000 games is evaluated relative to an objective benchmark that is based on the respective optimal move suggested by a chess engine. This provides a precise and comparable measurement of individual performance for the same individual at different ages over long periods of time, exploiting the advantage of a strictly comparable task and a comparison with an identical performance benchmark. Repeated observations for the same individuals allow disentangling age patterns from idiosyncratic variation and analyzing how age patterns change over time and across birth cohorts. The findings document a hump-shaped performance profile over the life cycle and a long-run shift in the profile toward younger ages that is associated with cohort effects rather than period effects. This shift can be rationalized by greater experience, which is potentially a consequence of changes in education and training facilities related to digitization.

The role of passage length on acoustic voice variability in bilingual speech

An individual's voice is determined in part by the limitations of their anatomy and physiology, in addition to language-specific phonological and phonetic structure. When a bilingual switches between languages, how much do they change their voice? Previous work using a corpus of spontaneous speech from early Cantonese-English bilinguals found surprisingly little variability across individuals' languages [Johnson et al., Proc. of Interspeech (2020)] compared to earlier research on across-talker acoustic voice variability [Lee et al., JASA (2019)]. A crucial difference between these two studies, however, is passage length. A longer passage (e.g., 30 min) potentially allows for a more stable structure to emerge in a principal components analysis, while a shorter sample (e.g., 2 min or less) may instead be subject to ephemeral variation, and potentially misrepresent the overall variability of a voice. Building on Johnson et al. (2020), the present study asks: to what extent does passage length impact the results of principal components and canonical redundancy analyses designed to elucidate within-talker (across languages) and across-talker (within language) idiosyncratic variation? These results are important for theories of talker recognition, identification, and discrimination, in addition to improving understanding of talker-specific acoustic-phonetic variation.

Peers, Gender, and Long-Term Depression

We provide first evidence that peer depression in adolescence affects own depression in adulthood. We use data from Add Health and an identification strategy that relies on within-school and across-cohort idiosyncratic variation in the share of own-gender peers who are depressed. We find a significant peer effect for females but not for males. An increase of one standard deviation of the share of own-gender peers (schoolmates) who are depressed increases the probability of depression in adulthood by 2.6 percentage points for females (or 11.5% of mean depression). We also find that the peer effect is already present in the short term when girls are still in school and provide evidence for why it persists over time. Further analysis reveals that individuals from families with a lower socioeconomic background are more susceptible to peer influence, thereby suggesting that family can function as a buffer. Our findings underscore the importance of peer relationships in adolescence with regard to the development of long-lasting depression in women.

Assessing Inter‐ and Intra‐reliability in Frontal Sinus Outlines

Human frontal sinuses are highly variable between individuals in terms of their size and shape. This idiosyncratic variation has been used in medicolegal fields for positive identification. Although qualitative comparisons are common practice, several 2D and 3D methods to objectively quantify their morphology have been proposed to statistically support such identifications. One approach has been to outline the superior border of the frontal sinus from traditional radiographs, using Elliptical Fourier analyses (EFA) of those frontal sinus outlines (FSOs) to characterize sinus shape. Several studies show this method quantitatively illustrates FSO uniqueness. To make such a method applicable to medicolegal cases, however, inter‐ and intra‐observer reliability in the tracing of FSOs must first continue to be evaluated.This study uses digital radiographs of 40 crania in Caldwell position from Des Moines University’s anatomical collection to assess inter‐ and intra‐observer variations in FSO tracings. Five crania had bilateral aplasia; two were too difficult to see. FSOs were traced in the remaining 33 crania by two researchers using ImageJ, with the superior orbital border demarcating the inferior boundary. FSOs were imported into SHAPE‐software, and underwent EFA (20 harmonics) and principal component analyses (PCA). PC1 (50.34% of the variance) reflected height‐vs‐breadth relationships, while PC2 (13.40%) reflected differences in outline complexity between researchers; ANOVAs confirmed these significant differences along PC2 (F=10.879; p<0.0001). Further investigation revealed that one observer tended to follow the lobe contours more detailed, tracing further into the septa between lobes. With this knowledge, a second set of tracings by the same researchers, both better accounting for complexity, were undertaken to assess whether more specific instructions can control for such deviations. Subsequent PCAs and ANOVAs indicated no significant differences in PC1 or PC2 within or between individual tracings (p‐values > 0.05). However, several FSO‐tracings still plotted relatively far apart along the PC1 and PC2 axes. These “problematic” sinuses were often smaller in size or had smaller lobes. Interestingly, the issue lies primarily with inferior border placement— not the sinus itself. In such cases, small lobes near the inferior boundary were not always included in the FSO‐tracing, greatly altering FS size and shape as captured by EFA.This information helps support the use of FSOs in forensic identification, but only when appropriate considerations are made. Similar to previous studies, these results indicate that investigators should be aware that FSOs of smaller sinuses may not be as reliable; this study also indicates large sinuses with smaller lobes may also be problematic. Intra‐ and inter‐observer reliability of the placement of the superior orbital border and potential errors beyond tracing deviations need further investigation to fully understand potential errors and any major implications in the use of FSO in medicolegal identifications, given the high stakes of misidentifying an individual or erroneously excluding a true identity.Support or Funding InformationFunding support provided by IOER‐Grant 03‐19‐01.

Spatial and temporal turnover of soil microbial communities is not linked to function in a primary tropical forest.

The spatial and temporal linkages between turnover of soil microbial communities and their associated functions remain largely unexplored in terrestrial ecosystems. Yet defining these relationships and how they vary across ecosystems and microbial lineages is key to incorporating microbial communities into ecological forecasts and ecosystem models. To define linkages between turnover of soil bacterial and fungal communities and their function we sampled fungal and bacterial composition, abundance, and enzyme activities across a 3-ha area of wet tropical primary forest over 2 yr. We show that fungal and bacterial communities both exhibited temporal turnover, but turnover of both groups was much lower than in temperate ecosystems. Turnover over time was driven by gain and loss of microbial taxa and not changes in abundance of individual species present in multiple samples. Only fungi varied over space with idiosyncratic variation that did not increase linearly with distance among sampling locations. Only phosphorus-acquiring enzyme activities were linked to shifts in septate, decomposer fungal abundance; no enzymes were affected by composition or diversity of fungi or bacteria. Although temporal and spatial variation in composition was appreciable, because turnover of microbial communities did not alter the functional repertoire of decomposing enzymes, functional redundancy among taxa may be high in this ecosystem. Slow temporal turnover of tropical soil microbial communities and large functional redundancy suggests that shifts in abundance of particular functional groups may capture ecosystem function more accurately than composition in these heterogeneous ecosystems.