Despite their reputation as symbols of baby-boomer America, Protestant megachurches attract a younger crowd and more singles than the average Protestant church, according to a large-scale study released Tuesday.

The survey also found that megachurch-goers volunteer less and give less money on average than other churchgoers.

From January through August 2008, the Hartford Institute for Religion Research at Hartford Seminary and Leadership Network surveyed nearly 25,000 people who attend 12 U.S. megachurches.

An estimated 5 million Americans a week attend roughly 1,300 U.S. megachurches, defined in the study as Protestant churches with attendance of 2,000 or more. For comparative data on Protestant churches of all sizes, the study relied on the U.S. Congregational Life Study of 2001.

Among the findings: