Discussion Papers no. 861

Identifying fertility contagion using random fertility shocks

Does the fertility behavior of one individual affect the fertility choices of another? This study aims to estimate fertility contagion net of unobserved heterogeneity, using sibling networks as an empirical example.

Fertility contagion through social networks increasingly attracts the interest of demographers. While these theories propose a causal mechanism, they are rarely put to test in a plausibly causal statistical design. This study applies quasi experimental techniques to distinguish network effects from selection. Using contagion between siblings as an empirical example, we draw data from Norwegian administrative registers (N approx.170 000 men and women). We use twin births and the sex composition of children as random fertility shocks. We find no consistent significant effects of random shocks to a sibling's fertility on ego's fertility. First born women have larger families over time if a younger sibling chooses to have three children, as captured by the same sex instrument. We find no evidence that similarity strengthens contagion.

About the publication


Identifying fertility contagion using random fertility shocks


Sara Cools and Rannveig Kaldager Hart

Series and number

Discussion Papers no. 861


Statistisk sentralbyrå


Discussion Papers



Number of pages


About Discussion Papers

Discussion papers comprise research papers intended for international journals and books. A preprint of a Discussion Paper may be longer and more elaborate than a standard journal article as it may include intermediate calculations, background material etc.