Leaders and Laggards: Who Signs the NPT?
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Political Variables
Democracy. We use the Polity IV data (Jaggers & Gurr, 1995) to test suspicions
that democracies may be quicker to sign the NPT than authoritarian states. Our measure
assesses democracy for each country-year: we create a derived measure of the level of
democracy within each state by combining the two separate eleven-point scales for
democracy and autocracy from Polity IV: dem
i
= democ
i
- autoc
i
.
Political Volatility. Higher levels of political uncertainty may encourage
governments to join the NPT today in effort to tie the hands of tomorrow’s leaders. To tap
volatility, we created an index of the frequency, over the preceding 10 years, of changes in
government and regime-type characteristics, drawing on regime-type data from Polity IV
(Jaggers & Gurr, 1995) and newly available leadership data.
Satisfaction with US Leadership. The United States is the chief “promoter” of the
NPT, so it stands to reason that closer ties with the US would both make shared
preferences more likely and render a country more responsive to diplomatic suasion. Yet
coming up with an indicator for satisfaction with US leadership covering 175 countries for
30 years poses insurmountable difficulties. As a proxy for satisfaction with the
international status quo, we employ the S-index measure (Signornino & Ritter, 1999) of
the similarity between alliance portfolios. This compares each country’s alliance portfolio
with that of the United States, taken to be the global hegemon throughout the period under
consideration. Although this is a crude proxy, we suspect that similarity of alliance
portfolios is correlated with satisfaction with US leadership, providing a reasonable, albeit
far from perfect, indicator.
Convention