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.