The $1.7 billion Melrose Credit Union claims the top spot in SNL Financial’s 2012 ranking of the 50 best-performing credit unions with more than $500 million in assets, according to a release from the Charlottesville, Va.-based financial data firm.

The Corpus Christi, Texas-based, $1.4 billion Navy Army Community Credit Union and Iowa City, Iowa’s $1.5 billion University of Iowa Community Credit Union finished second and third, respectively.

SNL ranked the best-performing credit unions for the 12-month period ending March 31 using six core financial performance metrics: ROAA, net charge-offs to average loans, operating expenses as a percent of operating revenue, delinquent loans as a percent of total loans, market growth and net interest margin as a percent of average assets.

To determine the rankings, SNL measured each institution’s standard deviation from the mean of each metric. The standard deviations, which were equally weighted, were then added together to calculate a performance score for each company SNL Financial said in its announcement.

To be included in the analysis, a credit union had to have total assets greater than $500 million as of March 31 and had to be well-capitalized with a net worth ratio of at least 7.0%. Based on these criteria, 400 credit unions were eligible for the ranking.

According to SNL, Melrose has grown its loan book year over year in every year going back to 1995, the earliest year for which the firm has data, and it has experienced positive net worth growth each year over the same period.

For the 12-month period ended March 31, Melrose demonstrated 15.6% loan growth compared to 2.1% in aggregate for all U.S. credit unions. Melrose is among a group of credit unions that provides exclusive lending services to New York City yellow cabs.

“While successfully growing loans, Melrose has exhibited good underwriting acumen, as it boasts the lowest percent of delinquent loans as a percent of total loans among ranked credit unions,” SNL said in its release.

Even with the growing loan portfolio and 22% share growth, Melrose posted the second-lowest ratio of operating expenses as a percent of operating revenue among the top credit unions.

The most efficient institution in controlling expenses is No. 30-ranked New York City-based $578 million Progressive Credit Union, which reported the lowest operating expenses as a percent of operating revenues at 34.1%. The median value of the top 50 institutions in terms of operating expenses as a percent of operating revenue is 64.6%.

With 3.19%, Progressive Credit Union also has the highest ROAA for the 50 top-ranked institutions, which have a median metric of 1.38%. Progressive’s best-in-class ROAA translated to the highest net interest margin to average assets for the period, at 4.89%.

The state of Texas claims the most credit unions in the top 50, with eight, followed by New York with six. Iowa, Massachusetts, Virginia and Washington each have three.