This is part of a longer essay on wage growth during recessions from a San Francisco Fed Economic Letter:

Measuring nominal wage rigidities

Researchers generally point to asymmetries in the distribution of observed wage changes among individual workers as evidence of nominal wage rigidities. Figure 2 plots an example of this type of wage change distribution in 2011. The dashed black line shows a symmetric normal distribution. The blue bars plot the actual distribution of nominal wages.

The figure’s most striking feature is the blue bar that spikes at zero, indicating the large number of workers who report no change in wages over a year. This spike stands out in the distribution of actual wage changes, suggesting that, rather than cutting pay, employers simply kept wages fixed over the year. This is supported by the large gap to the left of zero between the actual distribution of wage changes and the dashed black line representing the normal distribution. This gap suggests that the spike at zero is made up mostly of workers whose wages otherwise would have been cut.