The fundamental problem of the political Left seems to be that the real world does not fit their preconceptions. Therefore they see the real world as what is wrong, and what needs to be changed, since apparently their preconceptions cannot be wrong.

A never-ending source of grievances for the Left is the fact that some groups are “over-represented” in desirable occupations, institutions, and income brackets, while other groups are “under-represented.”

From all the indignation and outrage about this expressed on the left, you might think that it was impossible that different groups are simply better at different things.

Yet runners from Kenya continue to win a disproportionate share of marathons in the United States, and children whose parents or grandparents came from India have won most of the American spelling bees in the past 15 years. And has anyone failed to notice that the leading professional basketball players have for years been black, in a country where most of the population is white?

Most of the leading photographic lenses in the world have — for generations — been designed by people who were either Japanese or German. Most of the leading diamond-cutters in the world have been either India’s Jains or Jews from Israel or elsewhere.

Not only people but things have been grossly unequal. More than two-thirds of all the tornadoes in the entire world occur in the middle of the United States. Asia has more than 70 mountain peaks that are higher than 20,000 feet and Africa has none. Is it news that a disproportionate share of all the oil in the world is in the Middle East?

Whole books could be filled with the unequal behavior or performances of people, or the unequal geographic settings in which whole races, nations, and civilizations have developed. Yet the preconceptions of the political Left march on undaunted, loudly proclaiming sinister reasons why outcomes are not equal within nations or between nations.

All this moral melodrama has served as a background for the political agenda of the Left, which has claimed to be able to lift the poor out of poverty, and in general make the world a better place. This claim has been made for centuries and in countries around the world. And it has failed for centuries in countries around the world.

Some of the most sweeping and spectacular rhetoric of the Left occurred in 18th-century France, where the very concept of the Left originated in the fact that people with certain views sat on the left side of the National Assembly.

The French Revolution was their chance to show what they could do when they got the power they sought. In contrast to what they promised — “liberty, equality, fraternity” — what they actually produced were food shortages, mob violence, and dictatorial powers that included arbitrary executions, extending even to their own leaders, such as Robespierre, who died under the guillotine.

In the 20th century, the most sweeping vision of the Left — Communism — spread over vast regions of the world and encompassed well over a billion human beings. Of these, millions died of starvation in the Soviet Union under Stalin and tens of millions in China under Mao.

Milder versions of socialism, with central planning of national economies, took root in India and in various European democracies.

If the preconceptions of the Left were correct, central planning by educated elites who had vast amounts of statistical data at their fingertips and expertise readily available, and were backed by the power of government, should have been more successful than market economies where millions of individuals pursued their own individual interests willy-nilly.

But, by the end of the 20th century, even socialist and communist governments began abandoning central planning and allowing more market competition. Yet this quiet capitulation to inescapable realities did not end the noisy claims of the Left.

In the United States, those claims and policies have reached new heights, epitomized by government takeovers of whole sectors of the economy and unprecedented intrusions into the lives of Americans, of which Obamacare has been only the most obvious example.

— Thomas Sowell is a senior fellow at the Hoover Institution. © 2013 Creators Syndicate, Inc.