ANN ARBOR, Mich. -- Health care prices grew 1.0 percent in May 2013 relative to May 2012, the lowest rate in our data series, which extends back to January 1990. The 12-month moving average, at 1.7 percent, is the lowest since the same reading was recorded in September 1998. National health expenditures, which combines prices and utilization, grew 4.2 percent in May, and revised data for the first quarter of 2013 put spending growth at 3.8 percent, below the record low levels seen annually since 2009.