For most of history, next to no measurable growth in output per person occurred. What growth did occur came from rising population.This is not the case. Per capita economic growth was significant and economically transformative prior to 1750, according to the research cited by Gordon for the United Kingdom (PDF).
Far more importantly than what happened before 1750, Wolf republishes Gordon's "stair step decline" graph which shows rates of per capita GDP growth dropping from about 2.5% per year in 1950 to about half that a half-century later. As I have shown from multiple datasets, that trend is not supported by the data.
How might one fool oneself into thinking otherwise?
Which is correct? Well, they both are "correct" from a mathematical perspective. From an economic perspective, what the two graphs tell you is that the data is noisy and start and end points for analysis make a big difference. The different pictures also offer a warning about the perils of taking trends off of smoothed data.
But over the long term, is there evidence of a great slowdown in rates of per capita economic growth? The answer is no.
Martin Wolf has promised me that he'd take a look at the data himself, which I appreciate. As the motto of Royal Society says, nullius in verba. Mistakes can easily occur in any analysis. The important thing is what is done once they are recognized.