So this explains why LA disappeared since the counties there actually have some twitter active people living in it to help normalize it. When zoomed in, in the

So this explains why LA disappeared since the counties there actually have some twitter active people living in it to help normalize it. When zoomed in, in the east there seems to be some halo effect at work were rural counties around bigger metros (Dallas, Atlanta, North Eastern Seaboard), with a lesser volume of tweets (low sample size) appear more active. When zoomed out the 100th meridian population divide is as obvious as it could be. So At the global level normalization is pretty much not in effect. This might likely be caused by the not uniform distribution and size of counties in the US. A better approach might be binning in equal area regions, with a threshold for low sample sizes.