There was an east-european economist (I've forgotten his name) who claimed that technological progress is exponential at some fixed rate that differs by society. His idea was that the limiting factor was the creation of prototypes. You make one prototype and learn from it, and that lets you make the next prototype, and so on.

So he said that the progress kept up at the same rate during the Depression even though the new technology didn't have much of a market. Because they could afford to keep on building prototypes all through that time. After WWII a whole lot of new technology got released to the public. And the prototype-building went on at the same old rate.

It could be true. He at least made a somewhat plausible rationale.