Lower inflation will allow the Fed to stick with programs announced Thursday aimed at lifting the economy. If the Fed were worried that prices are rising too fast, it might have to raise interest rates.On Thursday, the Federal Reserve said it would purchase $40 billion of mortgage-backed securities a month until the economy and job market show signs of steady improvement. Fed officials also said they would keep short-term interest rates low, even after the acceleration of any economic recovery. Rising gas prices could make consumers more cautious about spending in the coming months. Gas prices averaged $3.87 a gallon nationwide on Friday, 16 cents higher than a month ago and just 7 cents below the 2012 average high. Automakers earlier this month reported the best sales in three years, after seeing rising demand for pickup trucks. The government's retail sales data contrasted with reports from the nation's largest retail chains. Many said things picked up in August, driven partly by back-to-school purchases. Sales at 18 retail chains rose last month by the most since March. Sales at Target rose 4.2 percent and increased 5.1 percent at Macy's. Gap Inc. posted a 9 percent jump in sales. Employers added only 96,000 jobs last month, below the 141,000 added in July and far below the average gains of 226,000 in the first three months of the year. The unemployment rate fell to 8.1 percent from 8.3 percent, but only because the number of people in the work force shrank. The economy is growing too slowly to spur greater job gains. The economy expanded at a 1.7 percent annual pace in the April-June quarter. That's down from 2 percent in the first quarter and 4.1 percent in the final three months of last year.