Children missing from the French census. How much, where and why?

France has implemented, since 2004, a new census method, a so-called “renovated” census, one of the objects of which was to improve the quality of the results. However, since then, a large and tendingly widening gap has been observed between the number of young children under the age of 1 according to censuses and births previously registered by the civil status services. How to explain such a phenomenon? Is this phenomenon geographically localized? To answer these questions, its geography and the various possible causes are examined.