Prolif is slow—nuclear weapons are time-consuming and states fear backlash

In 1963, President John F. Kennedy declared himself ‘‘haunted’’ by the expectation that the club of nuclear weapon states would grow to 15 or even 25 members by the mid-1970s, unless the world could come together on a global nuclear test ban treaty.1 Despite Kennedy’s efforts, his hoped-for Comprehensive Test Ban Treaty finally materialized only in 1996, and as of 2013 the treaty had still not yet garnered enough state adherents to enter into force.2 Nevertheless, there are fewer than 10 nuclear weapon states in the world today, 50 years after Kennedy’s dark prediction. Why are nuclear weapons arsenals still so uncommon? Political scientists have wrestled with this puzzle ever since the proliferation issue surged to prominence after the end of the Cold War. Despite its diversity of theoretical and empirical approaches, the political science literature has come to a rough consensus on the slow pace of proliferation. Simplistic ‘‘realist’’ arguments that ‘‘nuclear weapons are a wonderful deterrent, that’s why states love them’’3 have been falsified—as the realists themselves increasingly acknowledge. Instead, scholars of proliferation point out that most states are naturally reticent to take a step that could unleash highly uncertain and potentially revolutionary consequences. It is therefore actually quite easy to understand why most states are not seeking to obtain the bomb; what is harder to understand is why a handful of states still do seem to want it. The political science literature also emphasizes that, despite global technical and economic progress since 1945, building nuclear weapons systems remains complex, costly, dangerous, and potentially very time-consuming. Therefore, even among the small number of genuine nuclear weapons aspirants, failure to achieve their ultimate goal is at least as likely as success. Indeed, in recent decades the failure rate has sharply increased. The overall political science finding of the great proliferation slowdown needs to be recognized by policy analysts focusing on single countries of concern, such as Iran or North Korea. Proliferation is a serious problem, but there is no cause for panic.