  Using the recently introduced declination function, we estimate the net
number of seats won in the US House of Representatives due to asymmetries in
vote distributions. Such asymmetries can arise from combinations of partisan
gerrymandering and inherent geographic advantage. Our estimates show
significant biases in favor of the Democrats prior to the mid 1990s and
significant biases in favor of Republicans since then. We find net differences
of 28, 20 and 25 seats in favor of the Republicans in the years 2012, 2014 and
2016, respectively. The validity of our results is supported by the technique
of simulated packing and cracking. We also use this technique to show that the
presidential-vote logistic regression model is insensitive to the packing and
cracking by which partisan gerrymanders are achieved.
