Could US Federal Reserve impose negative interest rate?

www.cnbc.com

The current target federal funds rate is in between 0.25 to 0.5 percent but could Fed impose negative interest rate in US? According to the article publish by fortune.com the Chair of the Board of Governors of the US Federal Reserve Janet Yellen mentions that they will not ignore on ruling out the negative interest rates. But there must be a lot of research that needs to be done before it could be practiced in the U.S. The original goal of Fed is to increase the interest rate slowly to achieve the 2 percent inflation rate target and economic growth.

By: Max