Why Do Supply Disruptions Lead to Inflation? Survey Evidence from the COVID Pandemic

Firms tend to justify price increases as necessary to cover rising costs. However, standard models imply that firms not only adjust prices to cost increases, but also to changes in spending. We present a model where, instead, there is differential adjustment depending on the type of shock. The model is disciplined using a firm survey, which shows that, towards the end of the pandemic, price increases were primarily a response to higher costs. In contrast, firms report not reacting to higher demand to avoid upsetting customers. Supply shocks are responsible for most of the upward adjustment of prices.