The main objective of this study is to find out if it is optimal to have tertiary level of education for all workers among OECD countries. The findings show that, although higher education level means higher economic growth, it is not optimal for any economy to have all workers with tertiary education. The optimal level, which gives the highest level of output in the sample, is about 49.8 percent in model 1 and 3, and about 46.9 percent in model 2. The highest level of 55.17 percent of workers with tertiary education is found in Canada for the year 2015. Therefore, though higher levels of education leads to higher economic growth, there should be proportions of workers with lower than tertiary levels of education.