[vacri]

The 8-hour workday predates the modern idea of time and motion studies, so it's a bit hard to get those kinds of statistics in a meaningful context around productivity.

But for the sake of argument, the percentage would be very low, probably pretty much limited to professionals that could work their own hours. Most people were working poor, for whom the workday was 10-16 hours long, six days per week (in the Western world).

To give you an idea of the significant lenghth of prior work hours, http://en.wikipedia.org/wiki/Eight-hour_day has a pair of phrases: "Women and children in England were granted the ten-hour day in 1847. French workers won the 12-hour day after the February revolution of 1848."