Although GM since the 1920s has always offered economy models in the U.S. market (relative to that market's definition in any given decade), and had done research and development in the 1940s and 1950s in preparation for any potential rise of strong demand for truly small cars in the U.S. market, it has also been criticized over the decades for not doing enough to promote fuel efficiency in the U.S. market in the 1970s through 1990s. GM's response has been that it has always responded to market demands and that most Americans, despite anything they said to the contrary, did not actually demand (at purchasing-decision time) small size or fuel efficiency in their vehicles to any great or lasting extent. Although some U.S. consumers flocked temporarily to the ideal of fuel economy whenever fuel supply crises arose (such as 1973 and 1979), they flocked equally enthusiastically to SUVs when cheap fuel of the 1980s and 1990s temporarily shielded them from any downside to these choices.