Using population-wide data on inventors and their demographic characteristics, the paper analyzes trends and patterns by technologies in age, the level of education, and gender gap. We find that the education level of inventors has risen over time. We also find that the gender gap is closing but at slower pace than in other comparable areas of society. Much to our surprise, the average age of inventors has been falling in all areas, despite rising levels of education. To explain the latter finding, we suggest three mechanisms as alternatives to the burden of knowledge argument: 1) the burden of dynamic knowledge renewal, 2) new technological opportunities, and 3) a generally increased propensity to patent. We discuss policy and managerial implications of our findings.