The Chicago Fed national activity index is a weighted average of 85 monthly economic indicators and has an excellent coincident relationship with GDP. As the chart shows, recessions are signalled by the index falling below -1. Historically, this has usually occurred at the onset of economic contractions.

Preliminary January figures released today show the index above the trigger level, at -0.58. This is up from -0.69 in December (revised from a preliminary -0.91).