Investor and economic writer John Mauldin recently met up with me at the Nasdaq to talk about his new book, Code Red.

The Fed has done everything it can to keep interest rates low over the last five years. But how much evidence is there that it's worked? How do we know interest rates are lower than they would be if they Fed stopped buying bonds completely? 

I don't think we do

I asked John where he thinks interest rates should be. Here's what he had to say: