to determine the "levels of consumption, production, and price for each commodity in each region, the pattern of world trade flows, and the refinery capital structure and output in each region". A system dynamics economic model of oil price determination "integrates various factors affecting" the dynamics of the price of oil, according to a 1992 European Journal of Operational Research article. A widely cited 2008 The Review of Economics and Statistics, article by Lutz Killian, examined the extent to which "exogenous oil supply shocks"—such as the Iranian revolution (1978–1979), Iran–Iraq War (1980–1988), Persian Gulf War (1990–1991), Iraq War (2003), Civil unrest in Venezuela (2002–2003), and perhaps the Yom Kippur War/Arab oil embargo (1973–1974)"—explain changes in the price of oil." Killian stated that, by 2008, there was "widespread recognition" that "oil prices since 1973 must be considered endogenous with respect to global macroeconomic conditions," but Kilian added that these "standard theoretical models of the transmission of oil price shocks that maintain that everything else remains fixed, as the real price of imported crude oil increases, are misleading and must be replaced by models that allow for the endogenous determination of the price of oil." Killian found that there was "no evidence that the 1973–1974 and 2002–2003 oil supply shocks had a substantial impact on real growth in any G7 country, whereas the 1978–1979, 1980, and 1990–1991 shocks contributed to lower growth in at least some G7 countries." A 2019 Bank of Canada (BOC) report, described the usefulness of a structural vector autoregressive (SVAR) model for conditional forecasts of global GDP growth and oil consumption in relation to four types of oil shocks. The structural vector autoregressive model was proposed by the American econometrician and macroeconomist Christopher A. Sims in 1982 as an alternative statistical framework model for macroeconomists. According to the BOC report—using the SVAR model—"oil supply shocks were the dominant force during the 2014–15 oil price decline". By 2016, despite improved understanding of oil markets, predicting oil price fluctuations remained a challenge for economists, according to a 2016 article in the Journal of Economic Perspectives , which was based on an extensive review of academic literature by economists on "all major oil price fluctuations between 1973 and 2014". A 2016 article in the Oxford Institute for Energy Studies describes how analysts offered differing views on why the price of oil had decreased 55% from "June 2014 to January 2015" following