There is great debate surrounding the demographic impact of China’s population control policies and, in particular, the one-birth restrictions which have only recently ended. We apply a transparent statistical method to explore the consequences for fertility and total population size in a ‘synthetic China’ not subject to the two major population control policies implemented in the 1970s. We find that while the less restrictive ‘later-longer-fewer’ policy played a critical role in driving down fertility in the 1970s, the role of the ‘one-child policy’ and its predecessors was only modest. Had China continued with its policies as implemented in the 1970s and followed a standard development trajectory, it is likely that the path of fertility transition and total population growth would have been very similar to that seen over the past three decades.