Since 2007, on the eve of the banking crisis, through 2013, the last year we have data for, the largest credit unions in Philadelphia and its Pennsylvania suburbs -- 11 institutions with at least $400 million each in deposits and share accounts -- have boosted those deposits by a collective two-thirds, bringing their total to $11 billion, according to National Credit Union Administration data collected by SNL Securities LLC.

The area's banks, though still much larger, have boosted deposits by just 12% during the same six years, to a total of $108 billion, according to Federal Deposit Insurance Corp. data.

Deposits have doubled, or nearly doubled, at Broomall-based Franklin Mint Federal Credit Union -- up 93%, to $757 million; at Freedom Credit Union in Bucks County -- up 93% to $568 million; at America Heritage FCU in Philadelphia -- up 106% to $1.04 billion; at Citadel FCU in West Chester -- up 81% to $1.6 billion -- in those years. Deposits at the largest federal credit union in the region, Police & Fire, are up 59% to $3.5 billion.

The most rapid growth at the credit unions took place in the late 2000s, during and immediately after the banking crisis. Deposits have continued to rise, as have credit union loans, though at a slower pace, since 2000. (The FDIC doesn't break down bank loans by locality.)

What's going on? "From the 2007 subprime mortgage meltdown and the bailouts of 2008 to today, at a time when a number of large banks went belly-up, merged, consolidated, or were sold, credit unions flourished," insists John D. Unangst, president and chief execuitve of Franklin Mint Federal Credit Union, Broomall. He says consumers and small-business owners like the idea of banking with member-owned cooperatives that don't have to show a profit.

Big banks (Philadelphia's most popular include Wells Fargo, Citizens, TD) counter by offering sophisticated banking software for smartphones and other remote devices and tying customers closer by offering multiple bill-paying and account-monitoring services that are inconvenient to replace. They also continue to offer multi-state branch and ATM networks (though some, like Citi, have been shutting down whole regions). The number of small banks in the U.S. is dwindling as more are acquired in mergers than are founded each year.

But Unangst can also point to the rising number of people who are joining credit unions as members -- a total of 987,000 in the Philadlephia area, just at the 11 largest credit unions with more than $400 million in deposits. That's up from 763,000 in 2007.