Industry consultants J.D. Power and LMC Automotive reported on Thursday that the trend of year-over-year monthly U.S. sales increases is about to come to and end as U.S. sales for the month of May are predicted to be down 5.7 percent from the same period a year ago.

The consulting firms indicated that the seasonally adjusted annualized rate for May will be 17.4 million vehicles, down from 17.7 million vehicles in May of 2015. The forecast for new vehicle sales for all of 2016 has also been lowered to 17.7 million vehicles, down from 17.8 million units.

Jeff Schuster, head of forecasting for LMC Automotive said in the report that a number of variables are contributing to the decline in sales growth, including a slowdown in economic growth and volatility in the stock market.