Even though only about 3% of conventionally financed purchase loans and 2% of conventionally financed mortgage refinances met the definition of higher priced loans, the Fed found small banks and credit unions were more likely to originate them.

"For example, while small banks and credit unions accounted for about 18% of conventional home purchase loans, they accounted for about 59% of higher priced conventional home purchase loans," the Fed article reported.

Federal agencies defined higher priced mortgages for first lien loans as those with an APR 1.5 percentage points higher than the average prime rate.

In a background interview, one of the article's three research authors said he only analyzed and reported the HMDA data, and did not attempt to explain it.

For example, the author acknowledged researchers had not considered the possibility credit unions and small banks made more loans in low-income areas or that fields of membership limited credit unions' ability to lend. Those factors could skewed the numbers.

CUNA Vice President of Economics and Statistics Mike Schenk also noted the greater percentage of higher priced loans from credit unions and small banks in the data. But he observed credit unions and small banks were more likely to make loans in low income areas or to low- and moderate-income borrowers than large banks. These loans to presumably riskier borrowers would naturally carry a higher interest rate, Schenk said.

According to the HMDA data Schenk analyzed, small banks originated 26.7% of mortgage loans with low- and moderate-income borrowers, while credit unions originated 25.3% to LMI borrowers. Comparatively, large banks originated 24.1% to that market.

The numbers for LMI neighborhoods were similar: Small banks originated 11.7% of their mortgage loans in LMI neighborhoods, while large banks originated 12.3% in those areas and credit unions originated 13.3%.

Additionally, the article emphasized a historically high percentage of mortgage loans in 2014 were originated by institutions – predominately independent mortgage companies and credit unions – with no responsibilities under CRA.

"At the time of the CRA's enactment, federally insured banking institutions dominated mortgage lending and held nearly three-fourths of mortgage debt. Because the CRA applies only to banks and focuses in particular on banks' assessment areas, shifts in lending activity away from banks and their assessment areas may weaken the CRA as a tool for communities to help ensure financial institutions are making credit available and doing so in a safe and sound manner. Research has found that, during the housing boom, higher-priced lending and mortgage delinquencies were much more prevalent among loans originated by independent mortgage companies and by banks outside of their assessment areas compared with bank loans within their assessment areas," the article read.

According to the Fed's analysis, independent mortgage companies accounted for 47% of the nation's purchase mortgages and 42% of refinanced mortgages, the highest levels since 1995. Combined with the rise in mortgage originations by credit unions and small banks, the percentage of mortgages originated by large banks dropped significantly, the paper said.

"Essentially, the article included a not very subtle recommendation, supported by the HMDA data, that credit unions should be subjected to the CRA compliance," Olympia, Wash.-based consultant Marvin Umholtz wrote in his Oct. 25 "CU Strategic Hot Topics" newsletter.

However, the Fed author strongly disputed that assertion. He stressed researchers merely wrote about what existed in the data and did not assign any particular meaning to it.

Schenk recognized credit unions, small banks and independent mortgage companies made a greater portion of originations in 2014, but pointed out even without CRA requirements, credit unions held their own in lending to low- and moderate-income members.

"I think we have a very good story to tell and our numbers back that up," Schenk said. "Credit unions make a greater percentage of mortgage loans to lower income borrowers and in lower income areas than do almost all banks," he said.

And, he pointed out, they do that even with FOM restrictions that restrict their ability to lend.

John McKechnie, a partner in the Washington-based advocacy and strategy firm Total Spectrum, observed that even if some banking interests wanted credit unions to comply with CRA, they would face an uphill battle, particularly in the current political atmosphere.

"I just don't think there is much of an appetite right now for banker arguments about CRA for credit unions," McKechnie, a former CUNA lobbyist and NCUA official, said. "And even if they wanted to try, I don't think they have much of a case. The whole point of CRA was to correct a banker practice called redlining that credit unions can prove they don't do," he added.

NAFCU Senior Vice President of Government Affairs and General Counsel Carrie Hunt stressed that credit unions have been widely recognized by lawmakers and regulators for not causing the financial crisis and for their prudent business model.

"Today, credit unions continue to do a fantastic job in serving their members," she said. "In a bid to do even more, NAFCU supports all credit unions being able to add underserved areas to their fields of membership, in addition to changes to strengthen the credit union charter."