title: Matplotlib giving wrong tick label values when figure size is changed
body: <p>I'm using the following code to plot a matplotlib stack plot:</p>
  
  <pre><code>mpl.rcdefaults()
  
  fig, ax = plt.subplots()
  years = [1980, 1990, 2000, 2010, 2020]
  data = [
      [10000, 11000, 12000, 13000, 11000], [20000, 21000, 31000, 61000, 65000],
      [0, 10000, 30000, 100000, 90000]]
  
   ax.stackplot(years, data)
  
  ax.grid(linestyle='--', color='k', alpha=0.15, axis='y')
  ax.set_yticklabels([x / 1000 for x in ax.get_yticks()])
  
  width = 6
  height = width/1.6
  
  fig.set_size_inches(width, height)
  </code></pre>
  
  <p>This creates the following chart, with the correct y axis labels:
  <img src="https://i.imgur.com/yXkVr2U.png" alt="stackplot"></p>
  
  <p>However, when I change the size of the plot with <code>width = 4</code>, I get the following chart, where the y tick values seem to have halved for some reason:</p>
  
  <p><img src="https://i.imgur.com/JZCidfV.png" alt="stack plot with the y tick labels showing half the value they should be"></p>
  
  <p>What gives?</p>
  
  <p>Cheers!</p>