All these signs, statistical or anecdotal, tend to be clearest when the economy is growing fast, because they reflect spending that is sensitive to the state of the business cycle. Economists working in governments and central banks need indicators that give prompt warning of the trends, supplementing these with informal signs that can act as early alarm signals. By the time official stats are available, the last wave of specialty stores will have closed down — then it’s too late either to cool the boom or to temper the recession quickly by adjusting interest rates or using fiscal measures.
Better yet would be signals that can foretell the future of the economy, but there are fewer of these “leading indicators.” One of the earliest attempts to predict the business cycle looked at the pattern of sunspots. The British economist William Stanley Jevons argued in 1875 that sunspot activity was linked to subsequent weather patterns, and this in turn affected corn harvests. That sounds bizarre now, and was never a successful forecasting tool, but it was a not unreasonable attempt in an economy far more reliant on agriculture than ours is today.
Since then, stock markets have been the classic leading indicator, as investors are supposed to foresee the economic trends — with every incentive since they’re betting on them. But these days, greater skepticism about the rationality and efficiency of financial markets has undermined confidence in their predictive power.
Still, another standard financial sign of an impending downturn is the relationship between short- and long-term interest rates, known as the yield curve. Normally, this has an upward slope because investors need a higher return the longer their money is tied up. However, if they expect the economy to weaken soon, and the Federal Reserve to respond by cutting interest rates, the yield curve will slope down.