How trustworthy are electronic voting systems in the US?

I’ve recently written an article for the Royal Statistical Society on the trustworthiness of US voting systems. Here is an excerpt:

My statistical analysis shows patterns indicative of vote manipulation in machines. The manipulation is relatively small, compared with the inherent variability of election results, but it is consistent. These results form a pattern that goes across the nation and back a number of election cycles. I’ve downloaded data and verified the results from several states for myself. Furthermore, the manipulation is not limited to a single powerful operator. My assessment is that the data reveals multiple (at least two) agents working independently to successfully alter voting results.

You’ll find the article in its entirety, here:
http://www.statslife.org.uk/significance/politics/2288-how-trustworthy-are-electronic-voting-systems-in-the-us