Each of these indicators measures a different aspect of the economy. Because their movements tend to coincide with the overall movements in the economy, they are called coincident indicators.
Normally the coincident indicators move more or less together. During the current recession, two of the indicators showed the same pattern: employment and after-tax income. Both of these measures peaked in December 2007. Industrial production was the next to peak, in January 2008. Real manufacturing and wholesale/retail sales peaked last, in June 2008. Thus the business cycle peak was relatively easy to identify.