When should the Fed raise rates?

Paul Krugman Blog - NYTimes.com: "Okun’s Law suggests that it takes 2 points of GDP growth in excess of potential to reduce unemployment by 1 point. Potential growth is probably around 2.5. So say we have 5 percent growth for the next 2 years — which would be hailed as a stunning boom. Even so, unemployment should fall only 2.5 points, to 7.3. In other words, even with a really strong recovery (which almost nobody expects), the Fed should keep rates on hold for at least two years."