Cuba. Cuba has the most educated population in North America, more doctors per capita then almost any other nation. The only reason they're struggling is because America's embargo. They want stuff too.

Mostly this, although Vietnam is doing quite well, especially considering their circumstances.

Cuba is also really interesting...not thriving, to be sure, but you have to end the US blockade before you blame them for their own hardships. And in spite of everything, they have democracy like we've never seen in the west.

Edit: also what beejboytyson said about Cuba.

Meanwhile, if you want a historical example then look no further than USSR.

Russia went from a backwards agrarian society where people travelled by horse and carriage to being the first in space in the span of 40 years. Russia showed incredible growth after the revolution that surpassed the rest of the world:

• https://wid.world/document/soviets-oligarchs-inequality-property-russia-1905-2016/
• https://wid.world/document/appendix-soviets-oligarchs-inequality-property-russia-1905-2016-wid-world-working-paper-201710/

USSR provided free education to all citizens resulting in literacy rising from 33% to 99.9%:

• http://www.revolutionarydemocracy.org/archive/PubEdUSSR.htm
• http://www.revolutionarydemocracy.org/archive/anglosov.htm
• http://unesdoc.unesco.org/images/0000/000013/001300eo.pdf
• https://en.wikipedia.org/wiki/Likbez

USSR doubled life expectancy in just 20 years. A newborn child in 1926-27 had a life expectancy of 44.4 years, up from 32.3 years thirty years before. In 1958-59 the life expectancy for newborns went up to 68.6 years. the Semashko system of the USSR increased lifespan by 50% in 20 years. By the 1960's, lifespans in the USSR were comparable to those in the USA:

• https://en.wikipedia.org/wiki/Demographics_of_the_Soviet_Union
• https://www.rand.org/pubs/research_briefs/RB5054/index1.html

Quality of nutrition improved after the Soviet revolution, and the last time USSR had a famine was in 1940s. CIA data suggests they ate just as much as Americans after WW2 peroid while having better nutrition:

• https://www.scribd.com/document/430076844/CIA-RDP84B00274R000300150009-5-pdf
• https://artir.files.wordpress.com/2016/05/compar1.png?w=640

USSR moved from 58.5-hour work weeks to 41.6 hour work weeks (-0.36 h/yr) between 1913 and 1960:

• https://books.google.com/books?id=x8JYjwEACAAJ
• https://b-ok.cc/book/2669908/77497f

USSR averaged 22 days of paid leave in 1986 while USA averaged 7.6 in 1996:

• https://www.ilo.org/public/libdoc/ilo/1994/94B09_66_englp2.pdf
• https://www.bls.gov/news.release/ebs.t05.htm

In 1987, people in the USSR could retire with pension at 55 (female) and 60 (male) while receiving 50% of their wages at a at minimum. Meanwhile, in USA the average retirement age was 62-67 and the average (not median) retiree household in the USA could expect $48k/yr which comes out to 65% of the 74k average (not median) household income in 2016:

• https://www.ilo.org/public/libdoc/ilo/1994/94B09_66_englp2.pdf
• https://www.cbsnews.com/news/could-you-get-by-on-the-average-americans-retirement-income/

GDP took off after socialism was established and then collapsed with the reintroduction of capitalism:

• https://commons.wikimedia.org/wiki/File:Soviet_Union_GDP_per_capita.gif

The Soviet Union had the highest physician/patient ratio in the world. USSR had 42 doctors per 10,000 population compared to 24 in Denmark and Sweden, and 19 in US:

• http://www.sciencedirect.com/science/article/pii/0735675784900482 (sci-hub for access)

• USSR defeated a smallpox epidemic in a matter of 19 days https://www.rbth.com/history/331857-how-ussr-defeated-black-smallpox

• The Social Consequences of Soviet Immunization Policies https://www.ucis.pitt.edu/nceeer/1997-812-03g-Hoch.pdf

So, how do people who lived under communism feel now that they got a taste of capitalism?

• A remarkable 72% of Hungarians say that most people in their country are actually worse off today economically than they were under communism. Only 8% say most people in Hungary are better off, and 16% say things are about the same. In no other Central or Eastern European country surveyed did so many believe that economic life is worse now than during the communist era. This is the result of almost universal displeasure with the economy. Fully 94% describe the country's economy as bad, the highest level of economic discontent in the hard hit region of Central and Eastern Europe. Just 46% of Hungarians approve of their country's switch from a state-controlled economy to a market economy; 42% disapprove of the move away from communism. The public is even more negative toward Hungary's integration into Europe; 71% say their country has been weakened by the process.

• The most incredible result was registered in a July 2010 IRES (Romanian Institute for Evaluation and Strategy) poll, according to which 41% of the respondents would have voted for Ceausescu, had he run for the position of president. And 63% of the survey participants said their life was better during communism, while only 23% attested that their life was worse then. Some 68% declared that communism was a good idea, just one that had been poorly applied.

• Glorification of the German Democratic Republic is on the rise two decades after the Berlin Wall fell. Young people and the better off are among those rebuffing criticism of East Germany as an "illegitimate state." In a new poll, more than half of former eastern Germans defend the GDR.

• A poll shows that as many as 81 per cent of Serbians believe they lived best in the former Yugoslavia -"during the time of socialism". The survey focused on the respondents' views on the transition "from socialism to capitalism", and a clear majority said they trusted social institutions the most during the rule of Yugoslav communist president Josip Broz Tito. The standard of living during Tito's rule from the Second World War to the 1980s was also assessed as best, whereas the Milosevic decade of the 1990s, and the subsequent decade since the fall of his regime are seen as "more or less the same". 45 percent said they trusted social institutions most under communism with 23 percent choosing the 2001-2003 period when Zoran Djinđic was prime minister. Only 19 per cent selected present-day institutions.

• 75% of Russians have expressed increasingly positive opinions about the Soviet Union over the years. Only a small portion of those surveyed said they had negative associations with the Soviet Union. The economic deficit, long lines and coupons were named by 4% of respondents each, while the Iron Curtain, economic stagnation and political repressions were named by 1% each, the Levada Center said.

• Adult mortality increased enormously in Russia and other countries of the former Soviet Union when the Soviet system collapsed 30 years ago. https://archive.ph/9Z12u

• Former Soviet Countries See More Harm From Breakup https://news.gallup.com/poll/166538/former-soviet-countries-harm-breakup.aspx

The Free market paradise goes East chapters in Blackshirts and Reds details some more results of the transition to capitalism.