There’s a recent working paper by Alexandra de Pleijt and Jacob Weisdorf that looks at skill composition of the English workforce from 1550 through 1850. They do this by looking at the occupational titles recorded in English parish records over that period, and code each observed worker by the skill associated with their occupation. They use the standardized Dictionary of Occupational Titles to infer the skill level for any given occupation. For example, a wright is a high-skilled manual laborer, a tailor is medium-skilled, while a weaver is a low-skilled manual laborer.
The big upshot to their paper is that there was substantial de-skilling over this period, driven mainly by a shift in the composition of manual laborers. In 1550, only about 25% of all manual laborers are unskilled (think ditch-diggers), while 75% are either low- or medium-skilled (weavers or tailors). However, over time there is a distinct growth in the the unskilled as a fraction of manual laborers, reaching 45% by 1850, while the low- and medium-skilled fall to 55% in the same period. You can see in their figure 10 that this shift really starts to take place by 1650, while before the traditional start of the Industrial Revolution.
Looking at more refined measures, de Pleijt and Weisdorf find that the fraction of workers classified as “high-quality workmen” – carpenters, joiners, wrights, turners – rose only from 3.9% to 4.9% of the workforce between 1550 and 1850. These are precisely the kinds of workers that Joel Mokyr claims are the crux of the Industrial Revolution in England. They built, improved, adapted, and micro-innovated all the classic inventions of the IR. While they were only between 4-5% of the workers, and this proportion didn’t expand rapidly, given population growth the absolute numbers of these high-quality workmen went up by a factor of 4 between 1700 and 1850 (from about 200K to 850K).