GM Will Stop Reporting Monthly U.S. Car Sales

General Motors Co. says it will switch next month from reporting its U.S. vehicle sales every month to doing so on a quarterly basis.

GM contends that 30-day periods aren’t long enough to indicate true sales trends. The company notes that bad weather, temporary sales incentives and other seasonal factors can warp monthly sales totals and make year-on-year comparisons difficult.

U.S. carmakers made the same argument some 25 years ago when they stopped reporting sales every 10 days. The only U.S. carmaker currently reporting sales on a quarterly basis is electric car manufacturer Tesla Inc.

Whether other carmakers follow GM’s lead isn’t certain. But observers suspect an industrywide transition is likely to occur over the next few years. Automotive News points out that the move from 10-day to monthly reporting took about three years.

GM says it made its decision carefully and only after studying companies in other industries that report sales on a quarterly basis. The carmaker also analyzed about three years of data on stock trading around its own sales reports.

GM’s Canadian unit will continue to publicly report monthly sales results. Company operations in at least three markets—Brazil, China and Mexico—will continue to submit monthly sales figures to auto industry trade groups in their respective countries.