â€œWhites will become a minority of the American population by midcentury if not sooner,â€ states America Enterprise Institute scholar Charles Murray in his fascinating new book, Coming Apart: The State of White America 1960-2010. In repeating this claim, Murray (likely unintentionally) furthers a misconception about the country's shifting racial makeup and what it means for the future of the United States.

Murray's likely source is the much-ballyhooed 2009 U.S. Census report [PDF] that parsed certain immigration trends and fertility trends to reach that conclusion. But the claim that â€œwhitesâ€ will be a minority in America by 2050 implies an invidious view of the importance of ethnicity and race. â€œWhites,â€ by earlier definitions cherished by nativists, are already a minority in this country and have been for many decades. The successful amalgamation of previously scorned "races" is a testament to the ever-broadening inclusive tolerance of the American social project.

Letâ€™s take a brief tour through the history of race and immigration politics in this country: Shortly after the turn of the last century, many nativists feared that mass immigration was overwhelming the white â€œracesâ€ that had historically contributed the most to populating the nation. One of the most notable expressions of this racial anxiety was the classic 1922 anti-immigration screed by Saturday Evening Post correspondent Kenneth Roberts, Why Europe Leaves Home: A True Account of the Reasons which Cause Central Europeans to Overrun America. â€œThe American nation was founded and developed by the Nordic race,â€ asserted Roberts. â€œIf a few more million members of the Alpine, Mediterranean and Semitic races are poured among us, the result must inevitably be a hybrid race of people as worthless and futile as the good-for-nothing mongrels of Central America and Southeastern Europe.â€

In 1921, Congress passed the Emergency Quota Act that established the national origins formula that limited the number of immigrants admitted from any country annually to 3 percent of the number of residents from that same country living in the U.S. based on the 1910 Census. Roberts claimed that the 1921 restrictions were not enough.

â€œAfter 1880 the Nordic immigration was overwhelmed by the backward, unassimilatable, undesirable immigration from Eastern and Southern Europe,â€ he argued. Roberts was most particularly concerned about the influx of Jews into the country.

Inspired in part by Robertsâ€™ book, Congress passed the 1924 Immigration Act to change the national origins formula, limiting the annual number of immigrants to 2 percent of the number of people from any country who were already resident here based on their numbers in the 1890 Census. The national origins formula remained the basis of U.S. immigration law until 1965.

But, from the point of view of nativists like Roberts, such immigration restrictions would prove to have come too late. The â€œNordic racesâ€ have already been overwhelmed and mongrelized by the progeny of the â€œAlpine, Mediterranean, and Semitic races,â€ black Americans, and immigrants from south of our border.

Letâ€™s add up the numbers: Despite Robertsâ€™ warning about swarms emanating from Central Europeans, there are about 20 million Americans who trace their ancestry back to Slavic ethnicities, including about 10 million Polish Americans. And 6 million more identify themselves as Jewish. And surely Robertsâ€™ would despair that 26 million Americans can trace their ancestral roots back to the Mediterranean regions of Europe, mostly from Italy.

Roberts did admit that some people of Irish ancestry qualified as â€œNordic,â€ but anti-Irish sentiments among Protestant Americans ran high in the 19th century. Sociologists Jonathan Warren and France Twine in their study, "White Americans: The New Minority" [PDF], note that back in the 19th century, â€œThe Irish were seen as a separate race.â€ They cite other scholars who report, â€œInherited features like eye and skin color, facial configuration, and physique were often mentioned. Common adjectives such as â€˜low-browed and savage, groveling and bestial, lazy and wild, simian and sensualâ€™ were employed â€˜by many native-born Americans to describe the Catholic Irish â€˜race.â€™â€ In any case, some 40 million Americans today claim Irish ancestry.

Of course, African Americans are the group that for centuries against which being white in this country was always contrasted. So anxious were some to maintain a clear distinction between the races that in the early 20th century 18 states adopted laws that classified citizens as black if they had â€œone drop of Negro bloodâ€ in them. Today, some 42 million Americans identify as African American.

Nowadays, the growing number of Hispanics is what most concerns many people. The Census Bureau uses the terms Hispanic or Latino to refer to a person of Cuban, Mexican, Puerto Rican, South or Central American, or other Spanish culture or origin regardless of race. That group now comprises the largest â€œminority group,â€ numbering just over 50 million.

So adding up all of the â€œnon-whiteâ€ groups, one finds that they and their descendants now total 184 million out of 313 million citizens, constituting nearly 60 percent of the countryâ€™s current population. But how can that be? After all, the Census Bureau notes, â€œIn the 2010 Census, just over one-third of the U.S. population reported their race and ethnicity as something other than non-Hispanic white alone (i.e. "minority").â€ The answer to this conundrum is that Italians, Poles, Jews, and the Irish are now considered â€œwhite.â€

It is this fact that renders silly and nearly meaningless the pronouncement that â€œwhitesâ€ will be a minority in this country by 2050. By 2050, just as the earlier waves of Irish, Italian, Jewish, and Polish immigrants were assimilated, so too will todayâ€™s Hispanic immigrants and their descendants be. For all intents and purposes, Hispanics will become as â€œwhiteâ€ as Irish, Italians, Jews, and Poles.

Meanwhile Robertsâ€™ worst fear of the â€œmongrelizationâ€ of the races in America is being realized. The rising intermarriage rate between members of the arbitrarily defined and federally recognized ethnic groups demonstrates ever-lessening concern by Americans about this issue. It is my hope and belief that Americans of whatever ancestry living in 2050 will look back and wonder why ever did anyone care about the ethnic makeup of the American population. America is an ideal, not a tribe.

Ronald Bailey is Reason's science correspondent. His book Liberation Biology: The Scientific and Moral Case for the Biotech Revolution is now available from Prometheus Books.