Last month, Thomas Piketty released the World Inequality Report, revealing worsening income inequality in virtually every country and region. Most readers groaned: they typically view income equality as an unqualified good.

The shortcomings of this view hit me when last week I visited the Killing Fields museum in Cambodia. Pol Pot launched the greatest equalisation programme in history on assuming power in Cambodia after US soldiers left in 1975. Within three days, he drove all city folk into the countryside to do manual agricultural labour.

A sophisticated Paris-educated revolutionary, Pol Pot aimed to create the most equal communist regime. All communist regimes swore by equality, yet clearly, the cities were far richer than villages, and well-educated folk were richer and more influential than poorly educated workers and farmers.

To end such distortions of equality, Pol Pot decided that all city folk, above all highly educated ones, must be brought on par with villagers doing manual work. This was resisted, naturally, not only by those forcibly evicted, but also by dissidents within the Khmer Rouge. Pol Pot condemned all dissenters (including party colleagues) as traitors and enemies of the people, and ordered their liquidation to achieve true equality.

Pol Pot’s equalisation programme led to the killing of 3 million people in Cambodia

Such megalomania is common among dictators. Seeking Marxist purity, Pol Pot took the killing of class enemies to a new extreme. He murdered an astonishing 3 million of the country’s population of 8 million, a far higher murder ratio than anything Hitler, Stalin or Changez Khan dreamed of. All in the pursuit of equality, you understand.

The killers were often teenagers hired to do the deadly work in rural camps to which supposed enemies of the people were sent. Bullets were too costly to use on this scale, so killing was done with clubs and agricultural implements. Agricultural reapers became Grim Reapers. Babies’ heads were smashed against trees. Victims were ordered to dig pits, into which their dead bodies were later dumped.

The Indian Left was delirious with delight when US troops abandoned Cambodia and allowed the Khmer Rouge to take over. It believed the end of American imperialism would usher in a new era of equality and prosperity.

Well, Pol Pot certainly achieved unrivalled equality. Unlike many dictators who lived lavishly, he and his colleagues lived spartan lives, determined to maximise equality. If this meant mass killing, so be it. After all, every Marxist revolutionary in history had called for the liquidation of class enemies and traitors.

I doubt if Piketty can unearth good income data on Cambodia under Pol Pot. But if such data were available, Piketty’s methodology would surely show Pol Pot’s Cambodia as the most equal country ever. Some leftists might applaud. I can only shudder with horror.

Lesson: do not exaggerate the virtues of income equality. The Berlin Wall was built to prevent people fleeing from egalitarian East Germany to inegalitarian West Germany. People swam across shark-infested waters from Mao’s egalitarian China to inegalitarian Hong Kong. Nobody swam the other way. Millions voted with their feet for opportunity over equality. Forced equality can kill opportunity, and thus become an instrument of oppression, not empowerment. Equality of opportunity can be more important than income equality.

Extreme income inequality is bad. It should be reduced by taxing the rich at a progressive rate, and providing safety nets and upward ladders to the poor. But such income redistribution needs sanction by a democratic regime accountable to citizens. This does not happen in the “People’s Democracy” of Marxist regimes like Pol Pot’s. There, the “people” actually means the party; the party actually means the politburo; and the politburo actually means the dictator. Such awesome concentration of power can expedite forced equalisation of income, but this turns out to be hell, not heaven.

True equality is not just equality of income. It is also, crucially, about equality of opportunity, something sorely missing in India. Above all, it includes some equality of power, some checks on the ruler. Pol Pot, like many other Communist dictators, aimed at economic equality by monopolising political power. But this produced a different inequality, the inequality of power. Forget Communist rhetoric about creating equality: there can never be equality between those with guns and power and those without.

Of the three kinds of equality — of income, opportunity and power — the last two are the most important. Piketty should cover all three sorts of inequality.

He and other analysts should also view global income inequality. This is falling dramatically, thanks to the rise of China and India. Poor countries are catching up. To ignore this, while decrying within-country inequality, is dishonest. That merits a full, separate column.