Why cherry-picked years distort a decade
Launch library · evergreen read
Choosing a specific starting year for a comparison can dramatically change the story a chart appears to tell, even when the underlying data has not been altered in any way at all, simply because the chosen starting point happens to sit at an unusually high or unusually low point in a longer cycle.
This technique, deliberate or accidental, is one of the more common ways a technically accurate chart still manages to mislead: the numbers themselves are correct, but the selected window quietly determines whether the resulting trend looks like a decline, an improvement, or something roughly flat overall.
A useful defence is to deliberately check what the same chart looks like using a different starting point, ideally one chosen well before anyone had a particular argument in mind, since a genuine trend should hold up reasonably well regardless of which specific year happens to be used as the starting line.