This thesis empirically assesses the degree to which differential attainment of socioeconomic status in the form of occupational earnings changes over the life course for members of the 1958 National Child Development Study birth cohort and how their socioeconomic background in childhood influences the development of their occupational earnings. Specifically, this thesis seeks to understand the extent to which socioeconomic gaps between cohort members narrow, widen or remain rigid throughout the life course. To rigorously undertake this research, three papers form the basis of the investigation: 1. Multilevel modelling approach to analysing life course socioeconomic status and compensating for missingness 2. How does parental social mobility during childhood affect socioeconomic status over the life course? 3. Linear quantile mixed models for investigating life course occupational earnings distributions The contribution of this thesis to the research literature is unique in its treatment and modelling of the socioeconomic status outcome variable. Specifically, I treat the outcome variable as continuous and repeatedly measured over the life course thereby enabling a more fine-grained investigation of between-individual socioeconomic status heterogeneity over time. This treatment enables me to observe differentials within broad social classes and study both the change in adulthood socioeconomic status and legacy effect pertaining to childhood socioeconomic background. The heterogeneity I observe helps determine that the occupational earnings development between individuals does not converge over the life course from 1981 to 2013 (age 23 to 55) controlling for their socioeconomic background, sex at birth and region of residence. The main implication of the thesis is that there is no evidence of the childhood socioeconomic status gap narrowing in adulthood and that higher parental socioeconomic status up to the age of 16 only serves to widen such a gap over the life course. This represents the key finding of this study on a sample of people in Great Britain from the late baby boomer generation.