Dual axes

One popular but terrible idea is to draw a scatter plot or line plot with two different y-axes. This typically happens when you have two metrics with different units, and different scales that you want to plot against a common x-axis. The problem is that by changing the relationship between the two axes, you can tell almost any story that you want with the data.

Here you can see the stock prices of Microsoft (MSFT) and Amazon (AMZN) from 2017 to 2020. When you saw these in Chapter 3, each price had been adjusted to relative to the maximum for that company. That way each line was comparable. Here, the prices have been adjusted for dividends and splits but they have not been scaled relative to their maxima.

Adjust the vertical position (+) and steepness (*) of the slope for the AMZN line, then determine which statement is true.