Does the rentier state stifle democracy?

In the current issue of Comparative Politics, Michael Herb says no:

Abstract: It is widely thought that oil and democracy do not mix. Rentier states need not tax their citizens, thus breaking a crucial link between citizens and their governments and dimming the prospects for democracy. The link between rentierism and democracy is examined using a cross-regional dataset. Particular attention is paid to the possibility that there are both positive and negative effects of rentierism on democracy. Consistent support is not found for the notion that there is a net negative effect of rentierism on the prospects that a country will be democratic. Instead, democracy scores in the surrounding region are strongly correlated with a country's own democracy score.

This answer contrasts sharply with the widely cited 2001 World Politics article by Michael Lewin Ross:

Abstract: ....The author uses pooled time-series cross-national data from 113 states between 1971 and 1997 to show that oil exports are strongly associated with authoritarian rule; that this effect is not limited to the Middle East; and that other types of mineral exports have a similar antidemocratic effect, while other types of commodity exports do not.

The author also tests three explanations for this pattern: a "rentier effect," which suggests that resource-rich governments use low tax rates and patronage to dampen democratic pressures; a "repression effect," which holds that resource wealth enables governments to strengthen their internal security forces and hence repress popular movements; and a "modernization effect," which implies that growth that is based on the export of oil and minerals will fail to bring about the social and cultural changes that tend to produce democratic government....