A Quantitative Model of Non-Marriage and Fertility: Bargaining over Leisure

This paper introduces a new factor contributing to the decline in marriage and fertility: the growth of leisure technology. Over recent decades, high-income countries have experienced two notable shifts in household and family dynamics. First, there has been a significant decline in marriage rates and fertility. Second, time has increasingly been allocated to leisure activities. This paper presents a unified model of marriage and fertility, incorporating intra-household bargaining dynamics. The model, calibrated using data from Japan between 2019 and 2023, is employed to assess the impact of leisure technology growth on marriage and fertility during 2005-2009. The findings highlight that leisure technology growth makes single life relatively more appealing compared to marriage and parenthood. The model explains 21.1% of the decline in marriage and 73.1% of the decrease in fertility.

💡 Research Summary

The paper introduces a novel driver of the long‑observed decline in marriage and fertility in high‑income societies: the rapid growth of “leisure technology” such as video games, social media, and streaming services. The author argues that these technologies raise the utility derived from leisure, making single life relatively more attractive and reducing the incentives to marry and have children. To test this hypothesis, a dynamic structural model of household formation and time allocation is built and calibrated using Japanese data from 2019‑2023, including the Japanese Household Panel Survey (JHPS) and census information on marriage, fertility, earnings, and time use.

The model distinguishes individuals by stochastic life‑cycle length and heterogeneous market productivity (wages). In each period, single agents are randomly matched; a marriage occurs only if both parties expect higher joint utility than remaining single. Once married, couples allocate their finite 16‑hour daily time budget among market work, household work (including childcare), and leisure. The bargaining power within the household is a function of the relative wages of the spouses; the higher‑earning partner enjoys a larger share of leisure. Crucially, the utility weight on leisure is allowed to evolve over time, capturing the effect of leisure‑technology improvements. Two “penalty” parameters are introduced: a “marriage penalty on leisure” (the loss of leisure when entering marriage) and a “child penalty on leisure” (additional leisure loss after the first birth).

Empirical facts are first documented: (i) Japan’s age‑specific fertility rate has fallen steadily since 2000, reaching 1.47 in 2022, while the share of never‑married individuals aged 45‑54 rose to 25.8 % for men and 16.4 % for women by 2020. (ii) Survey data (National Fertility Survey) show that “enjoying hobbies” and “freedom of being single” rank among the top reasons for postponing marriage, especially among the 25‑34 age group. (iii) Event‑study regressions reveal that the first child reduces women’s leisure time more sharply than men’s, confirming a “child penalty on leisure.”

The structural parameters are estimated via Bayesian MCMC, jointly fitting observed marriage rates, fertility rates, earnings distributions, and time‑use patterns. The calibrated model reproduces the heterogeneous marriage rates by earnings, the observed gender gap in leisure loss after childbirth, and the overall dynamics of marriage and fertility.

Counterfactual simulations focus on the period 2005‑2009. By increasing the leisure‑utility weight (representing leisure‑technology growth) by 0.15, the model predicts a 21.1 % reduction in the marriage rate and a 73.1 % reduction in the fertility rate relative to a baseline without leisure‑technology change. A decomposition analysis attributes roughly 60 % of the observed fertility decline to leisure‑technology growth, with rising female wages accounting for 5‑10 % and reductions in household/childcare burdens contributing 8‑12 %.

The paper contributes to three strands of literature: (1) the macro‑economics of labor supply and the price of leisure, extending works such as Kopetsky (2011) and Aguiar et al. (2021); (2) the economics of marriage and fertility, building on dynamic marriage models like Greenwood et al. (2016) but adding an endogenous fertility decision and leisure choice; (3) intra‑household bargaining, following Knobel (2013) and Burda et al. (2013), yet endogenizing the marriage market itself.

Policy implications are discussed. Since the “marriage penalty on leisure” is driven partly by asymmetric bargaining power, policies that equalize leisure opportunities—e.g., public childcare, flexible work arrangements, or subsidies for leisure activities for low‑earning spouses—could offset the disincentive to marry and have children.

Limitations are acknowledged. Leisure technology is summarized by a single utility parameter, ignoring heterogeneity across platforms; the model excludes non‑marital cohabitation and non‑marital births; and the empirical analysis is confined to Japan, limiting external validity. Future research directions include (i) disaggregating leisure technology into multiple indices, (ii) extending the household formation framework to incorporate diverse family structures, and (iii) conducting cross‑country comparisons to test the generality of the findings.

In sum, the study provides a rigorous quantitative framework that demonstrates how the rise of leisure‑enhancing technologies can substantially explain recent declines in marriage and fertility, offering a fresh perspective for both academic inquiry and policy design.