One indicator all sexual behavior has not decreased is the Total Fertility Rate, or how many children each woman has over her lifetime on average. The TFR in 1980, before online access to erotica became prevalent was 1.785 and currently is 1.784—hardly any difference at all. Of course it went up and down year after year but the rate has been largely steady. And to have children it still takes sex in most cases.

On the other hand a survey (which requires honest reporting) from two years ago compared 2008 to 2019 (so a short term survey) and said adults were having less sex but the cause they named wasn't being sequestered, but quite the opposite. They were too busy. They also note that comfort levels in discussing sex increased and it could be more people are comfortable saying they were having less sex.