Improvements in Fuel Economy - Responsible Factors

Well, it turns out that a couple of factors gave rise to the improvement in fuel economy across board. The improvements started with weight, engine displacement as well as engine output measured in horsepower (HP). It is not clear why these changes happened - perhaps the war-induced effects of the Yom Kippur War of 1973 and the resultant price increase made automakers reflect changes that required fewer gallons of petrol. This hunch came to mind because of the 10 automakers that made these changes to their products (out of a total 32 manufacturers), about half of these were American.

As a result, there was a 179% change in the fuel economy of the same version of cars first manufactured in 1970 and subsequently in 1982 (the 173% above is because automakers who made no significant changes but still ended up with slightly better cars were filtered out) owing largely to design improvements in weight and engine displacement as well as output (HP).

In all, it is clear from the dataset that global political upheavals exert no mean pressure on manufacturing decisions of automakers.