The US Environmental Protection Agency was created in 1970 to implement and oversee this massive attempt to control the injection of pollutants into the nation's air. Individually tailored strategies were created to deal with mobile and stationary sources. While air quality has improved in the industrial nations, it has deteriorated in the developing nations. Historically air pollution control has been based upon a traditional command-and-control approach. Traditional regulatory policy has not been cost-effective either. The allocation of responsibility among emitters for reducing pollution has resulted in control costs that are typically several times higher than necessary to achieve the air-quality objective. The state implementation plan (SIP) spells out for each control region the procedures and timetables for meeting local ambient standards and for abatement of the effects of locally emitted pollutants on other states. Ambient standards set legal ceilings on the allowable concentration of the pollutant in the outdoor air averaged over a specified time period.