WASHINGTON (MarketWatch) - The downside to low inflation: Americans who collect Social Security won't get an increase in their monthly checks in 2016. Annual increases in Social Security are made every year based on changes in a component of the consumer price index known as CPI-W. The index fell 0.4% in the period used by the government to calculate the annual increase in cost-of-living adjustments, the Labor Department reported Thursday. The extra benefits normally would kick in on Jan. 1. Social Security recipients got a 1.7% cost-of-living adjustment in 2015, 1.5% in 2014 and 1.7% in 2013. The last time there was no increase was in 2010 and 2011. Inflation has fallen sharply over the past year mainly because of a plunge in gasoline costs. Yet while all Americans benefit, seniors tend to drive less and not save as much because of cheaper gas.