Hmm, and yet only two-thirds of the working age population chooses to work, and some of that is part-time, which reduces the amount of labor available to employers. Labor can also move between sectors, leaving some relatively starved of workers. People who accumulate enough savings can choose to retire early and have to be enticed back into the labor market with higher wages, if they can be enticed at all. That doesn't look like a fixed supply of working hours that must be sold at any price -- the supply looks somewhat elastic.

Edit: Sorry about the tone in my original comment -- tax incidence doesn't seem to be common knowledge and I failed to consider that you might be aware of it already.