There was a 3.4 percent increase in U.S. chain-store sales during this past week as compared with one year ago, reports say. The upswing noted in the week's retail sales has been the strongest since July 2007. The first week of March 2010, saw chain-store sales increasing by 2.9 percent as compared to the previous week. %% The increase in sales is being attributed to better economic climate which lent to positive consumer sentiments for the spring season. It is likely that these positive trends would see sales increase by 2.5 to 3.5 percent during March 2010, reports say.