Q: What is wrong with Communism?

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http://www.merriam-webster.com/dictionary/communism

Communism

A way of organizing a society in which the government owns the things that are used to make and transport products (such as land, oil, factories, ships, etc.) and there is no privately owned property

What are some weaknesses of communism ?

Communism, unlike capitalism, eliminates the price system as a means for allocating scarce resources. Under capitalism, buyers and sellers rely on a mutually agreed-upon price when exchanging goods and determining production levels. In a communist economy, however, the state determines what and how much is to be produced. This invariably leads to shortages of some goods and surpluses of others. Neither shortages nor surpluses are economically desirable.
Communism also eliminates incentives. People are motivated by incentives: workers by salaries and wages and owners by profits. Because the government controls production, there is no incentive to work harder to achieve higher wages, nor is there any incentive to undertake the entrepreneurial risks necessary to earn profit. Therefore, economic activity stagnates.
A stagnant economy leads to decreased prosperity for society. Technological advances cease as industry uses inferior methods. The result is decaying industry and infrastructure and a poorer society overall.
Finally, communism reduces personal freedom. To meet prescribed production goals, the citizens of a communist regime are forced to follow government mandates. Travel into and out of the country is severely restricted and political dissent is suppressed by militaristic police.

What is wrong with Communism?

Some say that communist governments make unrealistic promises. The communist ideal is for everyone to become prosperous, but that hasn't happened in nations that have adopted the ideology.
Communist states typically have dictatorships that cling to power without the consent of the governed by preventing legitimate elections. Authorities restrict personal freedoms, execute political dissidents, and sometimes engage in ethnic cleansing and other human-rights abuses. Secret police, government propaganda, state-run news media, censorship and public surveillance are common characteristics of a communist system. Critics consider such practices tyrannical.
Another allegation is that communist countries don't perform well economically. They have often achieved lower production than capitalist countries and failed to meet the needs of their people. Communist regimes also allegedly cause more damage to the environment. Opponents point to the former Soviet Union's emphasis on industry, the military and space exploration. Such endeavors create pollution and other undesirable ecological effects.
Opponents maintain that the theory behind communism is flawed. They reject Marxist ideology as utopian and unachievable and say it doesn't stand up under scientific analysis.