(FORTUNE Magazine) – Believe it or not, the recession the economists didn't call is history. So says Geoffrey H. Moore, and no one speaks with more authority about the economy's turning points. Moore, 77, is director of the Center for International Business Cycle Research at Columbia University. A student of business cycles since the late 1930s, he serves on the National Bureau of Economic Research committee (which he helped found) that officially dates recessions. He tells FORTUNE's Rob Norton why he is confident: The pessimists are looking at measures of economic activity that don't recover immediately. Recessions don't vanish into thin air within a few weeks or months. One reason this doesn't feel like a recovery is that we are not back to where we were when the downturn began in July of 1990. But that's what happens in recessions. I've tentatively fixed a date for the business cycle trough: May 1991. That would make the recession cover a ten-month period. And that's very close to the average length since 1940. Most of the measures of aggregate economic activity, which is what we look at to identify the peaks and troughs, have been going up over the past six months, although relatively slowly. The thing that makes me think the expansion will continue is that most of the leading indexes are showing growth, and some are quite a bit stronger than the aggregates of economic activity, like total employment or real GDP. Despite a slight dip in November, the leading index published by the Department of Commerce has almost fully recovered from its decline during the 1990-91 recession. Our center's long-leading index has been rising since January 1991 and has completely recovered from the slump it had during the recession. This index consists of indicators that have a lead, on the average, of at least 12 months before business cycle peaks and six months before business cycle troughs. They include bond prices, the ratio of selling prices to labor costs per unit of output -- an indicator of profit margins in manufacturing -- and the growth rate of productivity. We also have a short leading index that has indicators such as stock prices, the average workweek in manufacturing, and orders for durable goods. Both of the indexes started to rise a little before this recovery period began and have continued to rise since. Until they start to show significant weakness, my inclination is to say that the recovery is here and is very likely to stay with us.