In the eighteenth and nineteenth centuries, as the pace of technological progress increased before and during the industrial revolution, most scientific and technological research was carried out by individual inventors using their own funds. A system of patents was developed to allow inventors a period of time (often twenty years) to commercialise their inventions and recoup a profit, although in practice many found this difficult. The talents of an inventor are not those of a businessman, and there are many examples of inventors (e.g. Charles Goodyear) making rather little money from their work whilst others were able to market it.[citation needed]