Does the Acquisition of Nuclear Weapons Change States’ Behaviour?

Political scientist James Fearon has an interesting blog post on the political science blog, The Monkey Cage. In it, he asks, and then gives an answer to, the question “How do states act after they get nuclear weapons?” The issue, Fearon notes, is gaining increasing attention in the United States, given the alleged quest by Iran to develop nuclear weapons. The issue also resonates in Canada, with Stephen Harper recently affirming his fear of the Iranian regime acquiring nukes. From this CBC interview with Peter Mansbridge, Harper responds in the affirmative to Mansbridge’s characterization of an interview Harper had given a couple of weeks earlier on the issue of Iran’s quest for nuclear weapons:

…in your view, they [Iran’s regime] want nuclear weapons, and they would not be shy about using them.[see the exchange below]

In opposition to views like Harper’s are the views of what Fearon calls “proliferation optimists” such as the well-known realist Kenneth Waltz, who claims that contrary to our repeated expectations about the behaviour of post-nuclear states, the opposite has turned out to be true much more often than not. What does Fearon find empirically? First, he sets up what it is, specifically, that he is measuring:

The following graph shows, for each of the nine states that acquired nuclear capability at some time between 1945 and 2001, their yearly rate of militarized disputes in years when they didn’t have nukes, and the rate for years when they did.

Here is a graph of Fearon’s finding with his summary below:

China, France, India, Israel, Pakistan, and the UK all saw declines in their total militarized dispute involvement in the years after they got nuclear weapons.  A number of these are big declines.  USSR/Russia and South Africa have higher rates in their nuclear versus non-nuclear periods, though it should be kept in mind that for the USSR we only have four years in the sample with no nukes, just as the Cold War is starting.