A standard model with a production function concave in labor will tell you that the marginal productivity of labor, and hence the real wage, decreases as labor increases. This the core relationship in the Malthusian model and has been the reason brought forward why some have observed that England enjoyed relative prosperity after the many deaths due to the Great Plague (and why some think the same will happen to Africa due to the AIDS epidemic). Of course, empirical evidence is somewhat thin for such old times.
Ulrich Pfister, Jana Riedel and Martin Uebele add an new data point to this by construction measured of real wages in Germany for the years 1500 to 1850, which they compare to population size. And they confirm the above. The Thirty Year War, which lead to significant population loss, was a period of significantly higher welfare for the survivors than before. This kind of relationship weakened over time though, probably reflecting that new factors became important in production. And it appears this change happened before the typical date we set for the Industrial Revolution in Germany.