The thing to keep in mind that during the early 20th century the economy was global at that point. Therefore, even in the closed off economy of the Soviet Union there were repercussions when the Great Depression hit America on the other side of the globe. Keep in mind that not all of these were negative, either.

For example the Soviet Union benefited from the Great Depression by using surplus labor in western countries for specialists in the growing Soviet Union. The Soviet Union brought in engineers, contractors, and farmers, most from Western countries and a lot from the United States. In Kotkin’s book, Magnet Mountain, he describes that a great number of Americans were brought in to build the Soviet Union’s “Gary, Indiana,” at the time the largest producer of steel in the world. Also, in my own specialization there was a great many of farmers from the United States that were brought in to help develop the plan for “mega-farms” in the Soviet Union. These farms would be larger than even farms in the United States, and they used the specialization of the American farmers to plan and organize these farms using their experience. The ability to hire and move these men to the Soviet Union was likely easier because of the depression, the lack of work these people may have had, and in result made it so the Soviet Union could industrialize at a faster rate, and use American experience to do so.

There was also issues with the Great Depression as well. The price of grain dropped drastically which led to problems within the America, but also it reverberated throughout the world, even to the closed economy of the Soviet Union. The Soviet Union in a bid to acquire foreign currency was exporting grain, so that they then could buy industrial goods. Between 1929-1931 the export of grain went from 200,000 tons to 2 million tons. With the drop in price of grain it led to the Soviet Union having to sell more tonnage for the same price, which hampered growth. Couple this with the holodomor happening in 1932-1933 and the industry of the Soviet Union slowed.

Finally, if you consider forces outside of the Soviet Union the great Depression help lead to the rise of the Nazi party within Germany, which inevitably led to World War II which cost the Soviet Union the hardest, in the world.

The economy was obviously not nearly as impacted as market economies were, but it did have to adjust it's exports accordingly (Montifiore, 2005) and I recall that Soviet grain actually hit the US markets hard by devaluing the price, so the Soviets played somewhat of a destructive role in one aspect.

Some Americans immigrated to the USSR at this time to escape what they saw as the failure of capitalism, most would be executed before 1940.

The Soviet Union was generally doing quite well at the time, and its economy was actually growing considerably in some areas. Some people in the West actually spoke out in favor of communism, instead of capitalism, because the Soviets were doing so well.

The main reason for the economic growth at a time of worldwide decline is the fact that the country had undergone massive changes in recent years. Those changes were still happening but they were beginning to see great results from the modernization and industrialization. Stalin had launched his first 5 year plan in 1928, the country was in an economic upwards spiral at the time.

The USSR simply still had a huge potential for economic growth at the time, while the US and other Western nations had grown their economy beyond what could be sustained.