Happy 207th birthday! You're one of 226,504,825 Americans celebrating today. That's 11.5 percent more of us than were around a decade ago.

The most populous state was Virginia (747,610) in the first census (1790), and only 201,655 (5.1 percent) of us lived in cities.

Each of us consumed about 24.8 percent more poulty in 1980 than in 1970, and about 21.1 percent less coffee, tea and cocoa.

If you're a man, you earn about $20,521; a woman, about $12,083.

If you're under 50, you may be more apt to die from homicide, at least according to 1977 figures when 81.3 percent of homicide deaths were in that age category.

As of 1980, 53.3 percent of single mothers were on welfare, with the highest concentration (90.8 percent) in Hawaii and the lowest (18.2 percent), Nevada.

Illinois leads the states with the greater proportion (86.2 percent) of residents with fluoridted water systems. Utah has the lowest percentage (2.4 percent).

Women physicians spend an average of 17.8 minutes in "face-to-face" encounters with their patients; men physicians, 15.3 minutes.

Andrew Hacker, professor of political science at Queens College, New York, has been gathering facts like that "all my life," and has assembled his most recent collection in a book titled U/S, A Statistical Portrait of the American People (Viking Press/Penguin, $8.95 paperback).

His statistics, says Hacker, 53, help explain "what kinds of individuals we are and the ways we lead our lives, the similarities we share and how we differ from each other.

"My main concern is to demystify statistics for the average person . . . the person who is intrigued by numbers . . . the baseball fans of this country."

The United States, he says, "leads the world in collecting information, but most of it is dispersed in documents few citizens ever see." Although drawn from government reports, most of his figures have been recomputed -- on my home calculator" -- and categories recast so that "significance is readily apparent."

More on the District of Columbia and these United States:

* From 1970 to 1980, the largest population increases were in Nevada (63.8 percent), Arizona (53.1), Florida (43.3), Wyoming (41.6) and Utah (37.9).

* Virginia population rose 14.9 percent; Maryland, 7.5.

* The District's 1980 population was down 8.7 percent from 10 years before, to 637,651, making it the 15th most populous city.

* The median U.S. age is 30, which means half the population is older, half younger.

* The youngest median age -- 24.2 years -- is in Utah; the oldest -- 34.7 -- in Florida.

* In 1980, 330,000 babies were born in August -- more than in any other month. The fewest babies were born in February -- 272,000.

* The year before, there were 33,429 sets of twins and 1,202 sets of triplets or quadruplets born.

* The pill was the most popular method of birth control, used by 45.8 percent of all couples, followed by the condom (14.8), the IUD (12.9), rhythm (6.9), foam (6.1), the diaphragm (5.9) and withdrawal (4.2).

* Murder was the fastest-growing cause of death from 1961 to 1981, increasing 134.7 percent. There were 23,250 murders in '81.

* Also up: cancer (32.2 percent, to 425,010), influenza (28.2, to 3,170), suicide (18.5, to 26,010), heart disease (14.1, to 964,520).

* But fewer people were dying of ulcers, pneumonia, tuberculosis, asthma and syphilis.

* In 1977, 1,411 people died after falling down stairs, and 483 died falling into a hole (or "other opening in the surface").

* Between 1970 and 1980, per capita consumption of dairy products, meat, eggs and melons decreased. (Melon consumption fell 16.7 percent.) But Americans were eating more sugar and other sweeteners (up 9.9 percent).

* The number of persons living alone rose from 10,851,000 to 17,816,000 -- a 64.2 percent increase, five times the general population's growth rate. Eleven million were women; 6.7 million, men.

* Nevada led in divorces per 1,000 population with 486, followed by Arkansas (9.9), Wyoming (8.5) and Alaska (8.4). The fewest were in New York (3.1), Pennsylvania (3.0) and Massachusetts (2.9).

* The average hourly wage in 1980 was $6.66. For every $1,000 earned by a man, women earned as: postal clerks ($939), editors/reporters ($850), high-school teachers ($829), cooks ($734), sales clerks ($674), bank officers ($602).

* From 1970 to 1980, women made their biggest inroads as barbers (up from 4.7 percent to 15.7 percent of the work force), lawyers (4.8-12.8) and typesetters (15.0-34.5).

* The number of computer operators increased 346.2 percent from 1970 to 1980. Also up: teachers' aides (190.2 percent), lawyers (101.1), bus drivers (50.8).

* There were fewer tailors (down 61.2 percent), stenographers (50 percent) and newspaper vendors (39.6).

* In 1980, 20,095,000 Americans, or 23 percent of workers, belonged to labor unions.

* In reported cases of syphilis per 100,000 persons in 1980, Louisiana lead wth 33.9; North Dakota was the lowest, 0.3. For gonorrhea, Alaska had the high, 1,016,500, New Hampshire, the low 96.4.

* The nation's wealthiest county in 1979 was Cimaron in Oklahoma, where the per capita income was $20,100. Other leaders: Wichita, Kansas ($18,599), Loving, Texas ($17,882), Arlington, Virginia ($16,027). The figure for Montgomery County, Maryland: $13,541.

* The poorest county, Wade Hampton, Alaska ($2,737).

* The wealthiest metropolitan area was Reno, Nev. ($12,317), followed by Bridgeport, Conn.; Anchorage; San Francisco; Midland, Tex.; and Washington, D.C. ($11,313).

* Among the 46 largest cities, Washington residents paid the most local taxes -- an average of $1,280 each. Next was New York ($841), Boston ($708), San Francisco ($416) and Philadelphia ($413).

* The lowest taxes: San Antonio ($88).

* As of October 1980, the government employed 1,372 GS-16s to GS-18s, 85,076 GS-14s and 15s, 264,834 GS-12s and 13s, 150,942 GS-11s, 164,664 GS-9s and 10s, 156,430 GS-7s and 8s, 551,622 GS-6s and below.

* The government employed 47 ceramic engineers, 24 fish hatchery managers, 45 podiatrists and 26 theater specialists.

* A federal survey showed that 42 percent of the government's women employees claimed they were sexually harassed, as had 15 percent of the men.

* In 1977, the country had 80,449 elected officials.

* There were 9,686,940 arrests in 1980. The major categories: driving while intoxicated (1,303,933), larceny theft (1,123,823), general drunkenness (1,049,614), disorderly conduct (724,404), drug offenses (533,010).

* In North Carolina, 256 out of every 100,000 persons were serving time in a state prison as of June 1981. Next came South Carolina (247), Nevada (241) and Georgia (238). Maryland was ninth (199); Virginia, 14th (164); New Hampshire, 50th (39).

* Among widowed persons age 65 or over who remarried in 1979, 60.6 percent were men; 39.4 percent women.

* For all those widowed, the median age for the bride was 55.2 and for the groom, 61.7.

* Between 1972 and 1980, the proportion of college students age 25 or older rose from 27.9 percent of the total to 34.3 percent.

* Among divorced women in 1979, 8.9 percent were supposed to receive alimony; 6.4 percent did, with their monthly sums averaging $263.50.

* Almost everyone who lives in Nevada -- 78.7 percent -- moved there from another state. Next came Florida (68.7 percent), Alaska (68.4) and Arizona (67.5).

* The 1980 figures showed 46.6 percent of Maryland residents moved to that state, 40 percent in Virginia. In Pennsylvania, only 19 percent moved there from another state. The national average rate of residents from another state: 36.2 percent.

* The average one-way trip to work is 9.2 miles and takes 20.4 minutes, at an average speed of 28.3 mph. About half of workers travel less than five miles; 8.6 percent commute 25 miles or more each way.

* In 1960 a majority (61.4 percent) of women who headed households were over age 45, a majority (53.3 percent) had no children under 18, and most (51.7 percent) were widows.

* In 1980 most of the women who headed families (56.5 percent) were under 45, most had children under 18 (62.5 percent) and most (70.5 percent) were single, separated or divorced.

The most startling or significant statistics to Hacker?

* "The changes in households and families. Children seem to be going out of style." The proportion of married couples who had no children (defined as under age 18) grew from 42.5 percent in 1970 to 49 percent in 1980, a difference of 15.3 percent.

* "There are almost 400,000 people in federal prisons."

* "This country is becoming a lot less white, and the number of immigrants is adding up, particularly Asian and Latin American," which accounted for 41.1 percent and 41.9 percent of the 460,348 American immigrants in 1979.

* "The great inequity and imbalance in older remarriages. Men, it seems, just stick their heads out the door and ask, "Is there anybody there?" It's not so easy for women, and it's sad."