 The theory of emerging adulthood is specifically applicable to cultures within these OECD nations, and as a stage of development has only emerged over the past half century.It is specific to "certain cultural-demographic conditions, specifically widespread education and training beyond secondary school and entry into marriage and parenthood in the early or late thirties or beyond".Furthermore, emerging adulthood occurs only within societies that allow for occupational shifts, with emerging adults often experiencing frequent job changes before settling on particular job by the age of 30.