Charlie Szrom and Thomas Brugato look at the effect of oil in Russia. An excerpt:
We found that as the price of oil rose, the aggressiveness index increased: that is, the more valuable oil became, the more hostile Russian foreign policy became. The reverse was also true: when oil prices dropped in 2001 and 2002, so did Russia’s aggression. The relationship proved strongest at the annual level: a $1.48 increase in oil prices yearly correlated with an additional “point” increase in Russian aggression. Oil prices rose from $17.37 a barrel in December 2001 to $73.88 a barrel in September 2007; over that same period, the aggression index rose from 17 to 55.