When I visit my family physician, he starts by checking my vitals. It’s amazing how critical are simple things like blood pressure, temperature and pulse. We social scientists know that vital signs matter in organized religion, too. There are a lot of details we can look at, but basics such as how many people identify with churches, whether they attend services regularly, or apply their faith to their daily lives, are awful important. Here is what we know: the vital signs of American Christianity are in serious decline. Recently, I compared crucial vital signs for Americans aged 18 to 44,...