Patent applications roughly tripled between 1990 and 2010 and kept climbing after that, with the sharpest acceleration starting in the mid-1990s as the internet arrived and made a great many other inventions possible. Grants rose as well, but nothing like as fast, so the gap between the two series widens steadily across the chart.
A patent gives an inventor an exclusive right for a limited time, which is one of the main ways governments try to close the gap between the private and the social return on research. The slider drops the early years and rescales the chart, which makes the recent years easier to compare. These two series are read from the book's figure rather than from the Patent Office tables, so treat them as close to but not exactly the published counts.