Overall collections, that is, as a percentage of gross domestic product. Corporate income taxes, however, have declined quite a bit while social insurance taxes have increased substantially.
The plot looks somewhat flat, but going from 15% to 20% is a 33% increase. That is quite a bit. How about a plot of spending as a percentage of GDP over the same time? How about a plot of total tax burden by income level over time?
Search "Hauser's Law". It's illuminating in terms of the amount of tax revenue we can expect, regardless of the tax policy.