Economists don't know when the decade-long expansion, now the longest in American history, will end. But here are the indicators they will be watching to figure it out.

Last week's report on second-quarter gross domestic product showed that the economy slowed last spring. It also came exactly 10 years since the Great Recession ended, making this officially the longest expansion in American history. (Well, probably. More on that in a second.) So perhaps it's no surprise that forecasters, investors and ordinary people are increasingly asking when the next downturn will arrive.

Economists often say that "expansions don't die of old


Indicator 1: The unemployment rate


Indicator 2: The yield curve

Indicator 3: The ISM manufacturing index

Indicator 4: Consumer sentiment

Indicator 5: Choose your favourite