Well yeah I mentioned the last 8-9 years. But a lot of the shift already occurred with Bush: "Bush flipped 11 states that had voted Democratic in 1996: Arkansas, Arizona, Florida, Kentucky, Louisiana, Missouri, Nevada, New Hampshire, Ohio, Tennessee, and West Virginia" (source Wikipedia); 8 of those have turned very much Republican since then.

So while the number of swing states has reduced a lot in 2016, the strength of republicans in the south hasn't changed a lot since 2000.