For many years, children, the elderly and women who were or might become pregnant were excluded from clinical trials for new drugs. This has meant that many medicines are approved for adult use but not for children; also that dose rates for when given to children and adults who are elderly or from minority groups was a guessing game because of the lack of experimental data. The US Federal Drug Authority in December 2000 mandated that children be included in all drug research, and for a couple years it has been offering drug companies an extra six months of patent exclusivity if they do so.