Nice piece, thanks. I hadn't noticed HC's latest video, but am also a fan so look forward to watching the full thing.

An initial thought, though: there seem at least a couple of places where one can grant his facts yet argue his interpretation of these as "good" is backwards.

For instance, one can argue that lower preindustrial working hours reflect chronic underemployment and unemployment, one of that society's chief problems, and that industrialisation alleviated this problem (and even that this was one of the great initial benefits of industrialisation).

And HC's following point ought to be seen as evidence against the superiority of preindustrial life:

Notice how the workers were constantly eating. That was one of the perks of being a day laborer. Food was a worker’s biggest expense, and so part of their compensation was that  their employer would take care of the food for that day. It would be like if part of your compensation was that your boss paid your rent. It relieved a massive financial burden.

Essentially he's just pointed out that living standards were so low that the majority of budgets had to be spent just on food. 

Yes, that’s essentially the stylised model I use – i.e. I understand the long-run history of GDP per capita growth at the frontier as a transition from stagnation (/a very low rate) into sustained growth at a roughly constant rate. And it is very stylised (and I allow that the take-off may have been quite gradual), but I still think it works quite well as a basic framework.

And I agree that Romer’s backwards projection implies that the rate of GDP per capita growth at the frontier has increased over time; but it doesn’t prove that this took the form of a constant acceleration across all of history, rather than a roughly discrete acceleration (described above).

I don’t yet think that the Maddison data supports the idea of accelerating frontier growth across millennia. I think we need better country and year coverage to establish that claim. Better country coverage because the country at the frontier changes over time. Even if we see constant acceleration in country X’s GDP per capita growth rate between (say) 1-1800AD, it is unlikely that it was consistently at the frontier. We need to splice together data from various countries to get a timeseries of frontier growth. And better year coverage to avoid us relying on data points which may just so happen to be at a low or high point in a fluctuating cycle. We might have a higher estimate of GDP per capita in country Y for AD1000 than AD1, but I’d need more convincing to interpret that as long-run growth rather than our data point for AD1000 incidentally being a good year (or at the high point of a cycle which may span generations) and/or our data point for AD1 incidentally being a bad year (/low point in a cycle).

I disagree with (5), that the long-term historical pattern is acceleration (and more specifically, I don't think that the first three charts in your linked piece are sufficient to demonstrate this).

At the frontier, real GDP per person growth has remained remarkably constant for the past ~200 years.

The growth rate for the world might show acceleration, but I understand this as a compositional effect, as more countries leave the zero/low growth regime and experience rapid catch-up growth. But in the long-run each country's growth rate will converge with the roughly constant rate at the frontier. Eventually we'll run out of countries joining the modern growth regime, and I'd then expect world real GDP per capita growth to slow. This paper from Robert Lucas describes the dynamics I'm talking about - see Figure 3 in particular (world growth accelerates and then slows and converges to the rate at the frontier).

And due to the near universal pattern of the Demographic Transition, I'd also expect population growth to trend towards zero in the long-run. So I wouldn't expect acceleration in the growth rate of total GDP either.

(FYI, I'm repeating my reasons for being unconvinced of David Roodman's piece on accelerating growth, which are in also in this Twitter thread).

Hope this is helpful!

Should modernisation theory receive more attention in critiques and apologetics of economic development?