I am not sure of the %, I imagine it is not terribly large, but it is still there.
Other projects were built with student labor. University students were encouraged to provide volunteer work on such projects. They got on a train and traveled some place wherever help was needed. My father said it was quite fun. He spent a summer in Khazakstan, then another in Siberia.
While certainly prisoners were used in its construction, saying that it was "built with slave labor" is somewhat disingenuous. Perhaps you are saying that parts of it were built using prisoners, who were not paid for their services? If so, that is certainly the case.
1. http://en.wikipedia.org/wiki/Trans-Siberian_Railway#Construc...
http://www.amazon.com/Gulag-History-Anne-Applebaum/dp/076790...
The Gulag was created as a terrible economic experiment - that having a large body of "free" slave labour would be good for the Soviet economy.
There were huge, and often pretty pointless, projects built with slave labor and very basic tools - one example being the Baltic - White Sea Canal:
http://en.wikipedia.org/wiki/White_Sea_%E2%80%93_Baltic_Cana...
In the 90s in the US, I had to spend 40 hours "campaigning" for candidates, if I wanted to graduate highschool. I wouldn't really call that slave labor, but, I certainly learned a lot more by planting sprouts.
Source: http://eh.net/encyclopedia/article/tuttle.labor.child.britai...
In particular, I'm curious how you'll back up the "but a notable part of it was due to decreasing the number of people as well," considering USSR's population grew during the period you are describing [1].
1. http://en.wikipedia.org/wiki/Demographics_of_the_Soviet_Unio...
The population grew from 1926 to 1937, but not from 1930 to 1937 - which is the reason the producers of the 1937 census were sent to the gulag. See: http://en.wikipedia.org/wiki/Soviet_Census_(1937) And the discussion about Soviet population statistics in this: http://en.wikipedia.org/wiki/Ukranian_famine
I should also point out that during the 1920-1940 period the USSR did a lot of territorial expansion into the lands held by the Whites, and then later into the Baltic states and grabbing parts of Finland and Poland.
I'll admit, though, that given that we're talking about the industrialization period in general I shouldn't be talking about a decreasing population since over the whole early industrialization timeframe the population did rise even without considering conquest. I would have done better to day "but a notable part of it was due to keeping population growth down with the use of famines."
My great grandfather was one of the peasants you describe (his land was taken away). Although the state use of land was inefficient, it was not the continual famine that you imply. Food shortages occurred, but, they occurred under the Tsars as well. The industrialization that occurred pre and post WWII in the USSR seems pretty undeniable though.
First, I'm not quite sure you appreciate the cost of that industrialization. The USSR achieved fast extensive growth in its early years by forcing a very high savings rate. What does that mean? They exported lots of grain to buy machinery. Where did the grain come from? The peasants. What did the peasants do after their grain was taken? They starved. The general attitude during this time (which helped the Party consolidate power) was not so much of withholding food from dissidents, but rather withholding food from anyone who couldn't make a convincing case for how they were benefiting the party or the state. So most of the progress in bring up the USSR industrial capacity per person was due to increasing industrial capacity, but a notable part of it was due to decreasing the number of people as well.
Second, forced savings is a good strategy for playing catchup industrially when there are lots of obvious ways you can invest the savings (called extensive growth). Its possible to mess this up (see the Great Leap Forward) but if the beaurocrats are competent its possible. But when you've urbanized and need to start specializing more to keep growing the economy finding efficient ways to do so becomes harder (you're in intensive growth). Its here that government directed industrial policies tend to fail (or at least work more slowly than less directed solutions) due to coordination problems.