Reading Russia's War by Richard Overy, there were tables comparing the industrial output of Nazi Germany and the Soviet Union. From 1941-1944 Germany vastly outproduced the USSR in Coal, Steel and Aluminium. Only in Oil did the USSR maintain large superiority.
Yet in terms of military output, the USSR produced vastly greater numbers of planes, tanks and guns than Germany throughout the war. How?
The USSR had a much more intense wartime mobilization of their workforce. When it mattered.
The key area is in war-related industry, where from the start of the war until 1943 Germany only increased the workforce in miniscule (<1%) proportions (of overall available workers), where the Soviets increased theirs dramatically, from about half the German total (8% to 14.1%) at the beginning of the war to more than double by 1943, when the Germans have 14.2% to the USSR's 31%. At the same time they manage to match the German overall commitment of workers to the armed forces, both sides in 1943 sitting at around 23%.
The impressive numbers achieved by the Soviets are more than balanced by their incredible losses - in 1941 the Western Front (which took the brunt of Barbarossa) took 191% of its strength in irreplaceable casualties, 1942 was a longer campaigning year, but in all was even more damaging with the Red Army taking 28.9% of its total irreplaceable losses of the entire war (to 27.8% in 1941) - the entire Red Army of 1942 lost 133% of its strength in casualties (including sick and wounded).
The levels of mobilization on the Soviet side through 1942 were unsustainable, and it begins to cool during/after 1943 as more workers are devoted to domestic/reconstruction tasks. But at this point the war is inevitably won, except for the Germans, who throw in everything and the kitchen sink.
Think of it like the cyclist who starts his sprint too late, and his opponent has created too great a gap to overcome. By most standards the USSR should not have economically survived 1942. If things had gone any worse than they did (i.e. failure of Uranus, German success in Citadel, less aid from allies, no second front) they were fucked.
If you've got JSTOR access, see: Mobilization for World War II: The USA, UK, USSR, and Germany, 1938-1945 by Mark Harrison in The Economic History Review (May 1988); or Harrison's book: The Economics of World War II: Six Great Powers in International Comparison; or Absolute War, Chris Bellamy (p.473 'To the edge of the abyss').