Recently released data from the General Social Survey, sorted by what is called the RelTrad, shows that mainline Protestants are in the midst of a decades-long decline, and it has intensified in its most recent survey.
The top line shows mainline Protestant identification, and fewer say they go to churches affiliated with mainline denominations. The bottom line shows attendance, and now less than one of 33 people you meet on the street regularly attends a mainline Protestant church.
Both markers, self-identification and regular attendance, are imperfect, as are the GSS and the RelTrad, but these are among the most widely cited and trusted tool researchers use to measure religious trends. Those trend lines into the future gives us a glimpse of what could happen if patterns don’t change.
If the data continues along the same pattern, mainline Protestants have an expiration date when both trend lines cross zero in 2039.