<Tr> <Td> <Ul> <Li> Index </Li> <Li> Outline </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> Index </Li> <Li> Outline </Li> <Li> </Li> </Ul> <Tr> <Th> <Ul> <Li> History </Li> <Li> Types </Li> <Li> Classification </Li> </Ul> </Th> </Tr> <Ul> <Li> History </Li> <Li> Types </Li> <Li> Classification </Li> </Ul>

What term below is used as a measure of productivity