Gerrymandering is often given as one explanation of why the Democrats lost congressional seats to the Republicans. Is there any good analysis about how many seats were lost because of gerrymandering that happened after 2008? To what extent have changes in district lines resulted in the Republicans gaining more seats?
Based on the Cook Partisan Voting Index, the effect seems to be negligible.
Looking at the PVI for the 2010 election, which was the last one to be used under the old district boundaries, the Republican candidate outperformed their national result in 235 districts, whereas the Democratic candidate outperformed in 192 districts. 8 districts were even with the national result. Source
These numbers are not significantly different ahead of next year's midterms. The Republican candidate outperformed their national result in 238 districts, compared to 189 for Democrats. Again, 8 were even with the national result. Source
The swing here is only three seats, which in my opinion is not statistically significant.
According to analysis by the Associated Press, the GOP benefited a bit from gerrymandering:
The AP analysis also found that Republicans won as many as 22 additional U.S. House seats [in 2016] over what would have been expected based on the average vote share in congressional districts across the country.
The NYT shows that the effect was a bit less in 2012:
Most of the political-science-based estimates suggested that gerrymandering cost the Democrats a net of 7 to 12 seats in 2012 (with a few estimates coming in higher and lower).
Analysis by the Brennan Center concludes:
[A] new report from the Brennan Center for Justice at NYU School of Law finds that extreme partisan bias in congressional maps account for at least 16-17 Republican seats in the current Congress