Cohort Profile: Survey of Families, Income and Employment (SoFIE) and Health Extension (SoFIE-health).

Panel studies in Western countries have transformed and greatly improved understanding of many social, economic and health trends, such as the British Panel Household Survey and the Whitehall study in the UK, and the Household, Income and Labour Dynamics in Australia (HILDA) survey. In New Zealand (NZ) there are a number of birth cohort and population-specific longitudinal studies: the Dunedin multidisciplinary health and development study, the Christchurch health and development study, the Pacific Islands Family Study and the Health Work and Retirement longitudinal study. However, there was a need for a longitudinal study that covered all age ranges which could provide an understanding of the dynamics of the NZ economy and its interrelationship between the social and economic well-being of individuals, families and households and the factors affecting this well-being. Statistics New Zealand was granted funding from the Foundation for Research, Science and Technology (Government organization) in 1997 to conduct a feasibility study for a longitudinal survey of income, employment and family dynamics. Following the feasibility study, the Survey of Families, Income and Employment (SoFIE) study was developed and first went into the field in October 2002. SoFIE is a single fixed panel longitudinal survey with duration of 8 years. Information is collected once a year from the same individuals on income levels, sources and changes; and on the major influences on income such as employment and education experiences, household and family status and changes, demographic factors and health status. Every 2 years (Waves 2, 4, 6 and 8) information on assets and liabilities is collected to monitor net worth and savings. A successful bid was made to the Health Research Council of NZ by health researchers to have a battery of health questions in Waves 3, 5 and 7—giving rise to the SoFIE-Health sub-study.