2. INDIVIDUALLY RATIONAL, COLLECTIVELY DISASTROUS
We tend to think behavior that is justifiable on the individual level is also justifiable on the collective level, and vice versa. If eating the occasional sugary treat is fine for me it’s fine for all of us. And if smoking indoors is bad for me, it’s bad for all of us.
The dynamics of contagion in a pandemic do not work like that. If the case numbers in your part of the country are still relatively low—spoiler alert: They’re not—inviting five of your friends over for an indoor dinner party might not pose an unacceptably high risk for any one of you. As long as everyone is relatively young and nobody has serious preexisting conditions, the direct risk to your health is quite small.
But if everyone who isn’t at especially high risk held similar dinner parties, some percentage of these events would lead to additional infections. And because each newly infected person might spread the virus to others, everyone’s decision to hold a one-off dinner party would quickly lead to a significant spike in transmissions.
The dynamic here is reminiscent of classic collective-action problems. If you go to one dinner, you’ll likely be fine. But if everyone goes to one dinner, the virus will spread with such speed that your own chances of contracting COVID-19 will also rise precipitously.