If technology has arrived everywhere, why has income diverged?

That is the topic of a new paper by Diego Comin and Martí Mestieri, published in AEJ: Macroeconomics, here is the abstract:

We study the cross-country evolution of technology diffusion over the last two centuries. We document that adoption lags between poor and rich countries have converged, while the intensity of use of adopted technologies of poor countries relative to rich countries has diverged. The evolution of aggregate productivity implied by these trends in technology diffusion resembles the actual evolution of the world income distribution in the last two centuries. Cross-country differences in adoption lags account for a significant part of the cross-country income divergence in the nineteenth century. The divergence in intensity of use accounts for the divergence during the twentieth century.

I am struck by the strength of the two major stylized facts in this paper.  The mean adoption lag for spindles, classified as a 1779 technology, was 130 years, or in other words that is how long it took for the technology to move to poorer countries.  For ships, listed as a 1788 technology, the mean lag is 110 years.  Synthetic fiber is a 1931 technology, with a mean adoption lag of 29 years.  For the internet, a 1983 technology (is that right?), the mean adoption lag is only 6 years.

But the overall story is not so simple.  The more advanced countries use more of these technologies, and use them more effectively (“intensity”), and that gap has been growing over time.  Yes, Ghana has the internet, but it is Silicon Valley that is working wonders with it.  Some technology use begs more technology use.

If you calibrate those parameters properly, it turns out you can explain about 3/4 of the evolution of income divergence across rich and poor countries.