A research note on the increasing income prerequisites of parenthood. Country-specific or universal in Western Europe?

Traditional economic theories link male income to higher fertility and female income to increased opportunity costs. However, shifting gender roles and socio-economic changes challenge these assumptions, with evidence suggesting rising income prerequisites of parenthood in high-income countries. This research note examines the role of income in first childbirth for men and women from 2006 to 2020 across 16 Western European countries based on longitudinal data from the European Union Statistics on Income and Living Conditions and discrete-time logistic regressions. Results show that higher income consistently increases the transition to parenthood in all countries, with stronger effects for women. Over time, income has become a stronger predictor of parenthood. Widening fertility differentials across income groups are primarily driven by declining first-birth probabilities among lower-income men and women, supporting the hypothesis of increasing income prerequisites of parenthood. In four countries, the positive income effect for men weakens, which we interpret as a signal of changing gender roles. In one country, widening fertility differentials are driven by increasing fertility among high-income women, consistent with the argument of declining opportunity costs. Overall, findings suggest that the income prerequisites of parenthood have risen in high-income countries, strongly contributing to increasing income inequalities in fertility.