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THEY ARE A CHANGING

How to compare data that change over time

Medical staff are seen reflected on a clock inside a hospital in Mexico.
Reuters/Carlos Jasso
A more powerful way of interpreting data.
  • Dan Kopf
By Dan Kopf

Data editor

Comparing data across time isn’t always simple, but it’s usually necessary. A few classic tricks can make it easier to parse trend from noise.

When examining data trends, the primary tool in the spreadsheet wizard’s toolbox is indexing. When data are indexed, it means all of the data points are compared to their level at some particular point in time. That gives every trend the same starting point, and helps us properly compare data points across time in order to see them in context.

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