The survey asked about six risk-mitigation behaviors: mask-wearing, hand-washing, keeping six feet away from others, canceling social activities, avoiding crowds and avoiding restaurants.

In general, the older respondents were, the more of those measures they took. But as early as April, 70 percent of all those aged 18 to 29 reported wearing masks, while 84 percent of those older than 60 did.

By June, 86 percent of young Americans said they were wearing them while 92 percent of the seniors said they were.

Frequent hand-washing or sanitizing was equally popular, but it dropped slightly among all age groups from April to June as scientists realized that the virus was more likely to be transmitted by a mist of tiny droplets than by picking it up from surfaces.