From the 1950s, marketing began to shift its reliance away from economics and towards other disciplines, notably the behavioural sciences, including sociology, anthropology and clinical psychology. This resulted in a new emphasis on the customer as a unit of analysis. As a result, new substantive knowledge was added to the marketing discipline – including such ideas as opinion leadership, reference groups and brand loyalty. Market segmentation, especially demographic segmentation based on socioeconomic status (SES) index and household life-cycle, also became fashionable. With the addition of consumer behaviour, the marketing discipline exhibited increasing scientific sophistication with respect to theory development and testing procedures.