Cohort effect

Abstract: Drawing from the National Survey on Drug Use and Health (NSDUH; N = 611,880), a nationally representative survey of U.S. adolescents and adults, we assess age, period, and cohort trends in mood disorders and suicide-related outcomes since the mid-2000s. Rates of major depressive episode in the last year increased 52% 2005-2017 (from 8.7% to 13.2%) among adolescents aged 12 to 17 and 63% 2009-2017 (from 8.1% to 13.2%) among young adults 18-25. Serious psychological distress in the last month and suicide-related outcomes (suicidal ideation, plans, attempts, and deaths by suicide) in the last year also increased among young adults 18-25 from 2008-2017 (with a 71% increase in serious psychological distress), with less consistent and weaker increases among adults ages 26 and over. Hierarchical linear modeling analyses separating the effects of age, period, and birth cohort suggest the trends among adults are primarily due to cohort, with a steady rise in mood disorder and suicide-related outcomes between cohorts born from the early 1980s (Millennials) to the late 1990s (iGen). Cultural trends contributing to an increase in mood disorders and suicidal thoughts and behaviors since the mid-2000s, including the rise of electronic communication and digital media and declines in sleep duration, may have had a larger impact on younger people, creating a cohort effect. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Abstract: Following individuals sampled in a large-scale health survey for the development of diseases and/or death offers the opportunity to assess the prognostic significance of various risk factors The proportional hazards regression model, which allows for the control of covariates, is frequently used for the analysis of such data The authors discuss the appropriate time-scale for such regression models, and they recommend that age rather than time since the baseline survey (time-on-study) be used Additionally, with age as the time-scale, control for calendar-period and/or birth cohort effects can be achieved by stratifying the model on birth cohort Because, as discussed by the authors, many published analyses have used regression models with time-on-study as the time-scale, it is important to assess the magnitude of the error incurred from this type of incorrect modeling The authors provide simple conditions for when incorrect use of time-on-study as the time-scale will nevertheless yield approximately unbiased proportional hazards regression coefficients Examples are given using data from the first National Health and Nutrition Examination Survey (NHANES I) Epidemiologic Followup Study Additional issues concerning the analysis of longitudinal follow-up of survey data are briefly discussed

Abstract: Using pooled cross-sectional data from the Surveys of Consumer Finances, and new panel data from TIAA-CREF, we examine the empirical relationship between age and portfolio choice, focusing on the observed relationship between age and the fraction of wealth held in the stock market. We illustrate and discuss the importance of the well-known identification problem that prevents unrestricted estimation of age, time and cohort effects in longitudinal data. We also document three important features of household portfolio behavior: significant non-stockownership, wide-ranging heterogeneity in allocation choices, and the infrequency of active portfolio allocation changes. Based on a specification including age effects and time effects (excluding cohort effects) we find that equity ownership has a hump-shape pattern with age, while equity shares conditional on ownership are nearly constant across age groups. Based on a specification that includes age effects and cohort effects (excluding time effects), we find that equity portfolio shares increase strongly with age. Following the same individuals over time, we find that almost half of the sample members made no active changes to their portfolio allocations over our nine-year sample period, while the vast majority of those who did make changes increased their allocations to equity as they aged.