"probably" does not cut it.

The lie is the Soviets were bad economic managers. They pulled off the most incredible feat in industrialising their economy in less than fifty years, more liek twenty five useful years.

The millions of starved peasants, slaughtered "class enemies", exiled dissidents.... They were there too. Not pretty, not moral, not desirable, but incredible achievement nonetheless.

I am not sure, how in the context of such a system "efficiency" can be measured. But in raw capacity there has never been anything like it until the Chinese in the nineties and naughties with their own millions of starved peasants, slaughtered "class enemies", exiled dissidents....