The nation’s welcome mats have been doing a lot less welcoming lately. Although Americans have been spending much more time at home in recent years—an hour and 39 minutes more a day in 2022 than in 2003—they aren’t inviting other people in. The percentage of people who hosted or attended a social event on an average day has fallen by 50 percent over the past couple of decades. Socializing of any kind declined over that same period, and isolation rose. These days, it seems, home is where people