UPDATE: Please see this post for updated charts and observations on this subject.
Here is a graph of Arab coups by year and state. The frequency of coups in a given year and country is represented here, thus only years with coups and countries with coups are shown (the colors change according to country). An Excel graph, similar but more clear and pleasing will be posted shortly (as well will others showing different data). This data differs from the data from the previous coup posts in that it adjusts errors in counting coups (for instance in Yemen), and shows each coup, its year and its state while the previous charts represented coups only by month, state and decade. Errors will be corrected in later versions. More variables are still in the works. Corrections are welcome in the comments section.
Here are two graphs using the updated data.
Another, looking at coups by month (total):
By state totals: