The 1990 amendments to the Clean Air Act allowed the U.S. Environmental Protection Agency to begin regulating all recreational marine engines including PWC, as well as other off-road internal combustion engines. The agency began a dialogue with manufacturers in 1991, resulting in regulations that were enacted in 1996. These regulations, set to phase in between 1998 and 2006, are considered averaging standards, because they allow manufacturers to offset more-polluting engines in their product range by offering other engines that exceed the standard. California and subsequently New York have, in turn, adopted more stringent regulations than the federal standard. Subsequent to 2004 when the maximum emission reductions required by California became effective, the substantial majority of new PWC units sold throughout the United States have met the lower emissions standards established by California.