The smallest annual increase of any of the 20 cities is still about double the rate of inflation. The S&P/Case-Shiller 20-city index rose 5.9% compared to a year ago in the three-month period ending in March, a tick higher than the 5.8% gain economists expected. That was the strongest annual price gain since July 2014. The broader national index rose 5.8% for the year, the highest in 33 months. The 20-city index rose a seasonally adjusted 0.9% during the month, while the national index was up 0.3%.