Mansfield and Snyder are wrong
Vipin Narang 9 and Rebecca Nelson, Both PhD Candidates in Government at Harvard University, and Research Fellow at the International Security Program, International Organization, Spring, p. 368
The Mansfield and Snyder argument has gained plenty of high-profile traction but does the empirical evidence support the argument? We find in our study that it does not. In particular, we find few observations involving incomplete democratization, weak institutions, and war between 1816 and 1992. Furthermore, we show that the purported relationship between incomplete democratization and war rests entirely on a cluster of unrepresentative observations involving the dismemberment of the Ottoman Empire prior to World War I .Finally, we discover that the cases selected to support the hypothesis rarely involved incomplete democratization with weak institutions. This is not to say that incomplete democratizers face no risks—indeed, scholars have recently shown that these states face a serious increased propensity for state failure or internal conflict.6 But while incomplete democratizers may face a heightened risk of imploding, we show that there is scant empirical support for the argument that these states are at risk of exploding and becoming more belligerent members of the international system.