The Census Bureau Index of Economic Activity (IDEA) time series is presented in a process control chart. Control charts are useful because they help distinguish between variation that is
inherent in a process and is therefore expected versus variation that is unusual and, in many cases, unexpected. The IDEA combines measures from fifteen distinct monthly time series into
a single series that is then standardized to have a mean of zero and a standard deviation of 1.
Consequently, the centerline of the control chart is at zero. The chart highlights four distinct regions:
- Values falling within ±1 standard deviation of the centerline (darkest shade of blue).
- Values between ±2 standard deviations and ±1 standard deviation of the centerline (third lightest shade of blue).
- Values between ±3 standard deviations and ±2 standard deviations of the centerline (second lightest shade of blue).
- Values outside ±3 standard deviations of the centerline (lightest shade of blue).
The gray shaded time periods in the display denote recession periods, as defined by the National Bureau of Economic
Research. Read more at
https://www.nber.org/research/data/us-business-cycle-expansions-and-contractions
.
Percentage changes for each non-IDEA data series displayed in the graph are presented without error bounds. Many of these series are
subject to sampling and nonsampling errors. Information on the sources and extent of known variability in the component series can be
found by visiting individual sites for each series linked in the cards below the IDEA data visualization in the Briefing Room.