It's that time of the month again when auto manufacturers release their eagerly awaited U.S. sales figures for the previous month. General Motors(NYSE:GM) and Ford Motor (NYSE:F) both released their sales numbers last week. Ford Motor's U.S. sales declined 3.4% year-over-year in March, but the auto maker managed to beat the consensus estimate nonetheless. I have commented on Ford Motor's latest sales results here. General Motors also had to report a year-over-year decline in vehicle sales, although the decrease in sales was not as large as the one for Ford Motor. In March 2015, General Motors sold 249,875 vehicles compared against 256,047 vehicles in the same month last year. That's a decrease of 2.4%. Retail sales declined 5% year-over-year to 182,710 vehicles. General Motors' March sales drop of 2.4% missed the consensus estimate of 0.1% growth. Read more