The NAI is a combination of 85 disparate economic indicators that are calculated and combined into a single national economic heartbeat.
About this Viz
Think of this viz like the road the economy is on. In the middle is the road, a band of green. When the red line (NAI 3 month moving average) is within the road, things are humming along smoothly. However, as soon as it swerves off to the side (last year?), problems happen.