Yesterday I was using the Global Terrorism Database to check some suprisingly low figures on what percentage of terrorist acts are committed by Muslims. (Short answer: Worldwide since 2000, about 80%, rather than 0.4 - 6% as given in various sources.) But I found some odd patterns in the data for the United States. Look at this chart of terrorist acts in the US which meet GTD criteria I-III and are listed as "unambiguous":
The graphs look large and clear to me. They're about 570 pixels wide. Are you using a cell phone? I'm using Chrome.
Now that I think about it, even if other countries had a similar base rate of lone-wolf terrorists, I might not see any in 200 samples, because many of them have much higher rates of terrorism than ours (in some cases, a hundred times higher). Also, those with high rates probably can't do the detective work to attribute attacks to "Individual" rather than "Unknown".
Latest Firefox, and they're still unreadably blury...