Looking at this first graph, it is certainly true that the percentage of independent voters has grown in the last 22 years - going from 29% to 38% of the registered voters. This has mostly come at the expense of the Republican Party, which dropped from 31% to 24% in the same time period.
On the surface, this would seem to imply that the country is becoming less conservative and, by extension, more liberal. But is that true? The second part of that graph casts some doubt on the theory that the country has become much more liberal. Let's take a deeper look.
Those unaffiliated with a religion have become 6% less Republican and 2% more Democratic.
Gen X has become 8% less Republican and 4% more Democratic.
Millenials have become 7% less Republican and 4% more Democratic.
In other words, these graphs taken collectively appear to show that people are leaving the Democratic and Republican parties, but not changing their political views all that much.