As an even-numbered lanthanide, in accordance with the Oddo-Harkins rule, ytterbium is significantly more abundant than its immediate neighbors, thulium and lutetium, which occur in the same concentrate at levels of about 0.5% each. The world production of ytterbium is only about 50 tonnes per year, reflecting that it has few commercial applications. Microscopic traces of ytterbium are used as a dopant in the , a solid-state laser in which ytterbium is the element that undergoes stimulated emission of electromagnetic radiation.