The Federal Reserve announced it will start buying $60 billion in Treasury bills each month to help control the benchmark interest rate. The move comes after a bumpy September for money markets.

The move is a “purely technical measure,” the Fed said in a statement , but this is only the latest in a progression of potentially concerning signs. James Bullard, president of the St. Louis Fed, recently listed trade as an area of concern , retail sales slowed in September , and the yield curve continues to send mixed signals .