"(Eastern Europe was) fully comparable to the middle level underdeveloped countries of Asia, Africa and Latin America today."

Albert Szymanski - Is the Red Flag still flying? The political economy of the Soviet Union (1984)

As we can see from the study: Good - The Economic Lag of Central and Eastern Europe. Income Estimates for the Habsburg Successor States, 1870-1910 (1994), the Eastern European countries were at an incredibly underdeveloped, agrarian, semi-feudal stage of production.

Infrastructure was almost non-existent, urban centres were small and sparse, the overwhelming majority of people were illiterate, and had no schooling. The average person had next to no access to healthcare, leading to horrendous child mortality rates, epidemics, malnutrition, and a life-expectancy comparable more to Medieval times, than today.

With very few exceptions, people had next to no political rights, and were at the boot of fascist and monarchical regimes.

Before socialism, life expectancy averaged 32.3 years.

"A concentrated expression of these and other measures to raise the standard of living (for example, improvement of health care) was the enormous increase in life expectancy of the population (of the Soviet Union) to 69 - the level of the most developed countries in the world at the time."

G. I. Khanin - The 1950s: The Triumph of the Soviet Economy (2003)

Soviet industrial production averaged 11% growth per year from 1928 to 1940, something unheard of in any other country.

Source: Keeran, Kenny - Socialism betrayed. Behind the collapse of the Soviet Union (2004)

Soviet industrial output doubled from 1929 to 1933, the worst years of the great depression, after having suffered complete destruction, invasion, and sanctions.

"By the 1960s, the Soviet Union had gone from being one of the most illiterate places on the planet, to being, by some measures, one of the best educated.

It turned out more graduates per head of population than any of the European countries;"

Francis Spufford - Red plenty (2010)