ACE improved its ranking in Barron’s annual list of "America’s Best Companies," advancing to number 283 from 382 last year. To determine rank on its 500 best American companies list, Barron’s uses four measures to grade and rank the largest publicly traded companies in the U.S. and Canada (as measured by sales, and excluding companies that are restating financial data, operating under bankruptcy protection or delisting shares):

• Performance of the stock for the 52 weeks ended April 27, compared to performance of the Standard & Poor’s 500 index for the same period
• Median cash-flow return on investment (CFROI) for the past three years, stripped of the effects of inflation and accounting practices
• CFROI in the latest fiscal year compared with the three-year historical median
• Sales growth in the latest fiscal year, adjusted for acquisitions and divestitures

Companies in the top quintile in each category earn an A in that category, those in the bottom quintile, an F. Using these grades, Barron's calculates a total grade-point average, or GPA, for each company on a 4-point scale. In the case of tie GPAs, the "winner" is the company with the greatest change in CFROI (or cash-flow return on equity, for financial companies) in the past year.