Further, there is controversy surrounding the use of 1990 as a base year, as well as not using per capita emissions as a basis. Countries had different achievements in energy efficiency in 1990. For example, the former Soviet Union and eastern European countries did little to tackle the problem and their energy efficiency was at its worst level in 1990, the year just before their communist regimes fell. On the other hand, Japan, as a big importer of natural resources, had to improve its efficiency after the 1973 oil crisis and its emissions level in 1990 was better than most developed countries. However, such efforts were set aside, and the inactivity of the former Soviet Union was overlooked and could even generate big income due to the emission trade. There is an argument that the use of per capita emissions as a basis in the following Kyoto-type treaties can reduce the sense of inequality among developed and developing countries alike, as it can reveal in activities and responsibilities among countries.