The researchers [...] used responses from 4,155 people in 2009 and 4,547 people in 2018. Just two sample years or a regular sample within those dates? Discuss

The researchers [...] used responses from 4,155 people in 2009 and 4,547 people in 2018. Just two sample years or a regular sample within those dates? Discussed here before has been the significant drop in male heterosexual activity due to the growth of hookup apps post-Tinder around 2012 allegedly focusing a majority of the female partnering among a minority of men. It would be interesting to know if the survey here is merely reproducing some of that or if the decline has been reasonably linear between the two quoted sample years.