Three of four Americans live in metropolitan areas and pay for it by shelling out 54 percent more property taxes than their coutnry cousins, the Census Bureau reported today.

The bureau, in a survey of the nation's 79,862 local government units between 1975 and 1977, also found that the 155 million urban dwellers pay more for schools, social services, police and other government functions, including public employe salaries.

In its 826-page report, the Census Bureau noted that local property taxes averaged $313 a person within the 272 districts defined as metropolitan areas and only $203 outside those districts, a 54 percent diference.

The 58 million rural residents had 2.5 million government workers, one for every 23.2 persons and paid them an average monthly salary of $874. The 6.6 million urban bureaucrats -- one for every 23.4 city dwellers -- earned an aberage of $1,150 a month, 32 percent more than the rural officials.

Teacher salaries average $283 higher in cities, but city police officers earned $483 more than rural law enforcers. There were more teachers per 10,000 persons in the rural areas and more police and firemen per capita in the urban areas. Cities also employed three times as many people to look after parks and recreation for each 10,000 persons as did rural areas, but put proportionally one-third fewer people to work in hospitals and on highways.

California turned out to be the most urbanized state, with 92.8 percent of its population living in metropolitan areas of 50,000 persons or more. Vermont and Wyoming had no urban areas in 1977, and North Dakota was next to the bottom with 12.4 percent.

Rhode Island, New Jersey and Connecticut were all more urban than New York State, which came in fifth at 88.6 percent citified.

The bigger the city, the more is spent on government per person, the report showed. Cities of 3 million or larger in 1975 extracted $1,363.44 per person for local government spending, while cities of 50,000 to 200,000 demanded $765.84 or 44 percent less, from all sources of revenue. Noncity governments took in $722.25 per person.

Of that total, state governments provided $258 and the federal government $70, with the remainder coming from the rural authorities' own sources. In the cities, the federal government paid $101 per person and state governments $292.

Another Census Bureau study, released yesterday, showed the U.S. population has increased 8.3 percent since 1970, from 203,235,298 to an estimated 220,099,000 on July 1, 1979. As expected, the Northeast lost people to the south and West Sun Belt areas, with population in the Middle Atlantic states declining by 1.3 percent.

In percentages, the biggest gainer among the states was Nevada, with a 43.6 percent populaion rise since 1970, and the biggest loser by far was the District of Columbia, where the population declined over the period by 13.3 percent. Only in the number of persons over 65 did the D.C. population rise, and that by only 3.2 percent.

And 40.4 percent of all Americans are between 18 and 44, an increase of 24 percent over 1970 in that age category. The proportion of elderly persons is up nearly as much, 23.5 percent more than in 1970 and 11.2 percent of the current total.

Children between 5 and 17 years of age showed the largest decline, making up only 21 percent of the country now, 10.7 percent fewer than in 1970.