U.S. consumer prices were unchanged in October as a fourth consecutive decline in gasoline costs helped keep inflation tame, the government reported Thursday. The Labor Department said last month's flat reading of its consumer price index (CPI) followed a tiny 0.1 percent increase in September and a 0.2 percent drop in August. In the 12 months ending in October, CPI increased 1.7 percent, well below the Federal Reserve (Fed) target rate of 2 percent. In October, declining gasoline prices offset rising shelter and medical costs. Energy prices fell 1.9 percent, as gasoline prices tumbled 3 percent, while food costs rose 0.1 percent, the smallest monthly increase since June. Over the past 12 months, food prices are up 3.1 percent, one of the biggest gains for any category and a reflection of drought conditions in California. Excluding volatile energy and food costs, "core" CPI rose 0.2 percent last month after a 0.1 percent gain in September. Over the past 12 months, core CPI has risen 1.8 percent, also below the Fed 2 percent target rate. Declining energy and commodity prices amid a slowing global economy and a strengthening U.S. dollar are keeping inflation below the Fed target, economists say.