AFTER more than a quarter-century as a professional economist, I have a confession to make: There is a lot I don’t know about the economy. Indeed, the area of economics where I have devoted most of my energy and attention — the ups and downs of the business cycle — is where I find myself most often confronting important questions without obvious answers.

Now, if you follow economic commentary in the newspapers or the blogosphere, you have probably not run into many humble economists. By its nature, punditry craves attention, which is easier to attract with certainties than with equivocation.

But that certitude reflects bravado more often than true knowledge. So let me come clean and highlight three questions that perplex me. The answers to them may well shape the economy in the years to come.

How long will it take for the economy’s wounds to heal?

When President Obama took office in 2009, his economic team projected a quick recovery from the recession the nation was experiencing. The administration’s first official forecast said economic growth, computed from fourth quarter to fourth quarter, would average 3.5 percent in 2010 and 4.4 percent in 2011. Unemployment was supposed to fall to 7.7 percent by the end of 2010 and to 6.8 percent by the end of 2011.