biggest change in human history in terms of economy, lifestyle. Consider: if you were a guy from the middle ages randomly dropped into different centuries, you would recognize the basic lifestyle and economy and structure of life in every century but one. Whether in the 19th century or the 12th, you still pretty much use horses to do agriculture and written letters to communicate, etc.

This is not one event properly understood, but the fact that the way we do everything and the cost of everything looked totally different in 1978 surely means something.

Here is a podcast episode on the book: https://www.npr.org/sections/money/2017/05/19/529178937/episode-772-small-change

I listened to part of the audiobook, also. It is interesting. It has a lot of specifics. For example, he will consider transport and compare river transport to train. He not only shows that the cost per ton per mile drops, but that everything else also gets better: safety, reliability, availability. Another classic one is illumination. Not only does your cost per lumen drop over time, but the safety, reliability, ease of use, quantity available, excess heat released, odor, air quality etc. all improve so much that you can't even quantify it. 1978ers literally lived a hundred times more comfortably than 1878ers.

Back to your question: it would be nice to have a single event that contributes to this. The problem is that lots of events contributed. Also, some events punch above their weights if they trigger later events. I don't know if the treaty of Versailles gets to claim all credit for anything that was subsequently impacted by the later rise of the Nazis.