To illustrate this challenge of measurement and inference, Figure 7 presents Romanian birth rates before, during, and after the imposition of an infamously coercive policy aimed at raising births. In 1966, a dictatorial government imposed Decree 770, which banned abortion and made modern contraception effectively inaccessible. The figure extends an idea from Sobotka, Matysiak, and Brzozowska (2019), which compares cohort and period fertility rates in Romania over a similar evaluation window. We add data from Bulgaria, Romania’s neighbor that was also communist during the time of the policy and that might plausibly serve as a control, shedding light on what course Romanian fertility might have followed after 1967 if not for the policy. Panel A plots period birth rates in the two countries and shows that Romania and Bulgaria had substantially similar trends and levels in period total fertility rates before and after the Romanian policy window. Focusing on panel A of Figure 7, it is clear that birth rates in Romania changed dramatically following the start of the policy, as families were taken by surprise. TFR nearly doubled in the year that followed. The sharp timing of this apparent impact following the policy change, together with the availability of data from neighboring Bulgaria to serve as a control, suggests the possibility of a difference-in-differences analysis comparing birth rates pre– and post–Decree 770 in Romania and Bulgaria.

But while such an analysis could answer the narrow question of the causal effect of Decree 770 on the total fertility rate in 1967, it may nonetheless reveal little in terms of the impact of the policy on the number of children Romanian women had over their lifetimes. After the initial rise in TFR, birth rates soon began falling quickly in Romania, as behavior adapted to the new policy regime. If, for example, an unexpected pregnancy results in a birth at a young age in 1968, a woman may choose and succeed at reducing the probability of a pregnancy in subsequent years, and still achieve the same lifetime count of children.
For a discussion of the theoretically ambiguous impact of abortion restrictions on birth rates, see Lawson and Spears (2025). Of course, the extent of persistence from period fertility to completed fertility depends on the details: A shock that encourages earlier-than-desired births, as Romania’s might have, allows for adjustment later in life. But it may be harder, later in life, to adjust for a policy or event shock that leads to fewer births early in life.

Panel B of Figure 7 plots completed cohort fertility. As in earlier figures, cohorts are plotted along the horizontal axis according to the year in which they turned 30. Although Romanian completed cohort fertility began at a higher level than in Bulgaria over the available data series, completed cohort fertility in Romania did not maintain a sizable upward trend relative Bulgaria during the period that Decree 770 was in force.

That is from the recent Geruso and Spears JEP survey piece on whether we can expect fertility rates to rebound in the future.  By the way, after Hungary’s subsidy-driven baby boom, the country is now having a baby bust, it is possible that similar mechanisms are operating.