In 1944 there were approximately 7.5 million foreign workers (21% of the labour force) in Germany, mostly slave labour brought in from conquered territory. In the Soviet Union there were 20 million more women than men (In the postwar years, 1945-50, an average of 660,000 women entered the work force each year, as compared with 540,000 during the war). Nazi reprisal policies meant that there was village after village with no adult men over 15 at all left.

All economic aspects of especially the east were devastated by the war, not just a shortage of men but also horses and food. Places such as Poland and Yugoslavia would have effectively starved had UNRRA ( United Nations Relief and Rehabilitation Administration) food supplies not been distributed, quoting Tony Judt in 'Post-War':

UNRRA food supplies played a vital part in feeding Yugoslavia especially: without the agency’s contributions, many more people would have died in the years 1945-47. In Poland UNRRA helped maintain food consumption at 60 percent of pre-war levels, in Czechoslovakia at 80 percent.

Women were as I said now heavily relied upon, however there were other ways that the shortage was made up as much as it possibly could. Millions of people were "repatriated" to the Soviet Union in the years after the war - by 1953 for example 5.5 million "Soviet Nationals" were back behind the curtain, many of whom were organised into labour battalions. Partisans, Nazi camp inmates and others such as hundreds of thousands of Hungarians and even Germans were deported to the east by the Red Army, sent to the gulag and labour battalions.

Adolescents and older workers also stayed in the work force. The proportion of wage earners in the oldest and youngest age groups declined, but there was little or no decrease in absolute terms, given the 12 million (43 percent) increase in the labour force in the 1945-50 period. The number of pensioners employed in the national economy rose from 400,000 in 1945 to 484,000 in 1946, presumably in response to high food prices and low pensions. The Labour Reserves system, mobilizing adolescents for labour training and work in production, expanded in the immediate postwar years, rising to a peak in 1948 before dropping off sharply in the early 1950s.

During the Fourth Five-Year Plan (1946-50), 3.6 million students passed through the Labour Reserves system, which thus supplied around 30 percent of all labour recruitment in the period.

Labour was only one area of the economy where radical measures were taken to shore up eastern states, after Nazi spoliation came the dispossessing of the German populations in places such as Poland and Czechoslovakia. Again quoting at length from 'Post war':

The post-war dispossession of the German populations from Poland to Yugoslavia completed the radical transformation that had begun with the Germans’ own removal of the Jews. Many ethnic Germans in the Sudetenland, Silesia, Transylvania and northern Yugoslavia owned significant holdings in land. When these were taken into state hands for redistribution the impact was immediate. In Czechoslovakia, goods and property seized from the Germans and their collaborators amounted to one-quarter of the national wealth, while the redistribution of farmland alone directly benefited over 300,000 peasants, agricultural labourers and their families.

Gulag labour was of course an easy way of making up the numbers, even during the war Gulag labour produced perhaps 15% of all Soviet ammunition, large quantities of uniforms and items such as coal and oil required for the war machine. During and post-war the Gulag system could always be 'replenished' with more arrests or the deportation of captured prisoners of war or partisans and "collaborators" caught by the Red Army and sent east.

The gulag population, as Figes says, rose by 1 million in the years '45-50, with an additional 2 million German POWs used famously in the construction of the Volga-Don canal system. One 'bonus' of this kind of labour was that it was obviously unpaid, with very little needing to be spent on making them particularly comfortable.

Soviet plans to use German POWs as forced labor to rebuild Soviet cities and the economy...Soviet interest in economic exploitation of Germany was enormous. On May 11, 1945, Stalin instructed Malenkov, Molotov, Gosplan head Nikolai Voznesensky, Maisky, and other officials that the transfer of Germany’s military-industrial potential to the Soviet Union must be carried out with maximum speed to ensure economic recovery of the industrialized areas, ‘‘particularly [the coal mines of] Donbass.” During the discussion, Molotov stressed that the Soviets must strip West Berlin of all its industrial assets before its transfer to the Western powers. ‘‘Berlin cost us too much.”

Under Stalin there could always be a fresh supply of forced labour simply through denouncements and mass-arrests:

In December 1952, Stalin told a meeting of the Central Committee that ‘every Jew is a potential spy for the United States’, thus making the entire Jewish people the target of his terror. Thousands of Jews were arrested, expelled from jobs and homes, and deported as ‘rootless parasites’ from the major cities to remote regions of the Soviet Union. Stalin ordered the construction of a vast network of new labour camps in the Far East where all Jews would be sent.

"Russification" campaigns post-war in the Soviet borderlands, notably in the Baltic states of Estonia, Latvia and Lithuania. The Russian people were above all praised for their "great sacrifices which ensured decisive victory" - placing Russians at the front above all others rather than elevating Soviets. What this meant in practise is that hundreds of thousands of Estonians, Latvians, Lithuanians and Ukrainians were deported into Russia, mostly Siberia and Kazakhstan.

To sum up then, like in Germany a rapid influx of women into the workforce, mass arrests, POWs and citizens of satellite nations deported and pressed into forced labour and the spoliation of Germany and of Germans possessions in formerly occupied countries such as Czechoslovakia. Various international programs such as the UNRRA to ensure that people did not starve in the immediate aftermath as much as possible.

I hope this is enough for now, I can amend this later as I do not have access to all of my books and my memory of some of them is patchy to say the least.

EDIT: I am going to append some data which I think would be interesting for anyone who comes across this:

APPENDIX I

Rural & Urban Populations of the USSR in millions, selected years 1926-1950:

	Total Population	Absolute -	- Numbers	As % -	-of total
		Urban	Rural	Urban	Rural
1926	147	26.3	120.7	18	82
1939	170.5	55.9	114.6	33	67
1940	194.1	63.1	131	33	67
1950	178.5	69.4	109.1	39	61

:- 1939 does not include the incorp of western territories

:- 1940 does include incorp of western territories

l----------------------------------------------------l

The History of the Gulag: From Collectivization to the Great Terror by Oleg V. Khlevniuk

A Failed Empire: The Soviet Union in the Cold War From Stalin to Gorbachev (The New Cold War History) by Vladislav M. Zubok

Revolutionary Russia, 1891-1991: A Pelican Introduction by Orlando Figes

Postwar: A History of Europe Since 1945 by Tony Judt

International Labour and Working-Class History Volume 35 issue 1989 Fitzpatrick, Sheila -- War and Society in Soviet Context- Soviet Labor before, during, and after World War II