The article discusses the relationship between effective labor supply—determined by factors that are linked either directly or indirectly with human capital—and sustained economic growth per capita. On the basis of an expanded Mincer wage equation, the author estimates effective labor supply, taking into account effects linked with human capital, and conducts an econometric analysis of changes in the average working time in Poland in 1970-2005. The author zeroes in on long-term relationships and checks the results of his analysis against a body of statistical data. The diagnostic tools used by the author include the Gauss-Markov theorem, a method for evaluating statistical errors developed by mathematicians Carl Friedrich Gauss and Andrey Markov. According to Florczak, standard labor supply analyses are often inaccurate because they overlook factors linked with working time, the quality of labor, and the overall social and demographic conditions. In an era of globalization, the author says, if it wants to maintain its international economic competitiveness, Poland should increase the role of “extensive” factors of production by boosting the economic activity of the population.