What’s Ben Bernanke thinking? With this series of charts, we’ll help to explain why the Fed left interest rates at near-zero levels and kept intact its $85 billion a month bond-purchase program.

Read more on the Fed’s decision and Bernanke’s news conference.

First, a review of where we are. Interest rates have been at near-zero levels since the recession.

That’s not all. The Fed has bought about $3 trillion worth of mortgage-backed (shown above) and Treasury securities. This chart shows what has happened to mortgage rates, an area where Bernanke is clearly happy.

And what’s all this easy policy got? There have been job gains, and the unemployment rate has come down. But not enough to Bernanke & Co.’s liking. The Fed say the jobless rate has to get below 6.5% before they’ll even think about lifting interest rates.

Here’s another measure of the jobs market, called the quits rate. Bernanke and the Fed’s vice chair, Janet Yellen, want to see this rate increase. Why should they want people to quit? Well, that would be a sign they are leaving to take either a better job or set up on their own — a bullish signal. The quits rate is still well below pre recession levels.

And why can the Fed afford to be so loose? So far, inflation hasn’t overheated. This is the central bank’s preferred measure of inflation (and yes, it includes food and gas), and it’s well below the Fed’s 2% target.

It’s not just Bernanke who thinks Fed policy is going to be easy for some time. Two-thirds of the Fed’s members (including those who don’t have a vote this year) don’t expect a rate hike for another two years. Now, the Fed may stop bond purchases before that — most economists expect the rate of bond purchases to slow if not stop sometime this year.