I thought this article by Yegor Gaidar, based on his talk at the American Eneterprise Institute in November 2006, was an interesting and straightforward explanation for the end of the Soviet empire: complications from the need to import grain and the need to earn foreign currency by exporting oil. Consider this excerpt:
Yet one of the Soviet leadership's biggest blunders was to spend a significant amount of additional oil revenues to start the war in Afghanistan. The war radically changed the geopolitical situation in the Middle East. In 1974, Saudi Arabia decided to impose an embargo on oil supplies to the United States. But in 1979 the Saudis became interested in American protection because they understood that the Soviet invasion of Afghanistan was a first step toward--or at least an attempt to gain--control over the Middle Eastern oil fields.
The timeline of the collapse of the Soviet Union can be traced to September 13, 1985. On this date, Sheikh Ahmed Zaki Yamani, the minister of oil of Saudi Arabia, declared that the monarchy had decided to alter its oil policy radically. The Saudis stopped protecting oil prices, and Saudi Arabia quickly regained its share in the world market. During the next six months, oil production in Saudi Arabia increased fourfold, while oil prices collapsed by approximately the same amount in real terms.
As a result, the Soviet Union lost approximately $20 billion per year, money without which the country simply could not survive. The Soviet leadership was confronted with a difficult decision on how to adjust. There were three options--or a combination of three options--available to the Soviet leadership.
That's an interesting explanation. What are the lessons learned? From the conclusion:
We may not be "fighting" the Cold War at present, but we are still cleaning up the battlefield.
In this latter case, it becomes evident that the "contract" between authoritarian rulers and their subjects--which secures stability by people's tolerance of the authorities and the authorities' noninterference in people's affairs--will need to be reexamined. Such reevaluation undermines the regime. The rulers, who for the longest time have insisted that their rule is the best, find it hard to ask for and get broad societal support in a moment of crisis. In this situation, the society has a habit of answering, "For many years, we were told that we are led to a ‘brighter future,' but now you would like us to tighten our belts. Instead, tighten your belts--or leave."
Russia does not need new upheavals. During the course of the twentieth century it saw enough of them. In this regard, the understanding by the elites and society that a real democracy is not an ideological dogma or something imposed by the West, but rather an important precondition for the stable development of the country, will finally give Russia the hope of escaping crises and cataclysms. This realization is vitally important for Russia's development in the next decades.