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Covid-19 is a reminder to beware of seasonality in data

A couple walks amid fallen leaves of Chinar trees in a garden on an autumn day.
Reuters/Danish Ismail
A season for change.
  • Dan Kopf
By Dan Kopf

Data editor


From immigration patternsย to household spending to music listening, coronavirus is turning 2020 upside down.

In the US, most of that change occurred between February and April, which makes looking at trends tricky. Many data points change from February to April every year, so to understand the magnitude of a change it is necessary to compare it to what happened in previous years. In other words: Beware of seasonality.

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