On 1 January 2017, the population of France was 67 million, an increase of 0.4% with respect to 2016. The total fertility rate continued to drop in 2016, notably among women aged 25-29, the age group with the highest fertility. The number of residence permits issued rose slightly and reached its highest level since 1998. Newly arrived foreigners with a residence permit represented 0.32% of the French population on 1 January 2015, compared to 0.30% the previous year. Unlike the number of civil partnerships (PACS), the number of marriages – both different-sex and same-sex – continued to decline. Mixed nationality couples (one French and one foreign partner), who account for 18% of new unions, have a larger age gap between partners than couples where both partners are French. After a severe flu epidemic in 2015, mortality fell back again in 2016. The gender gap in life expectancy narrowed slightly in 2016, to 6.1 years. Demographic behaviours differ greatly from one département to another, probably because of social and economic disparities, as well as geographic differences (notably whether or not the département is located on a border), and cultural differences that influence mortality and union formation.