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Inequality in access to dental services in a market-based dental care system: A population study from Norway 1975-2018.

OBJECTIVE
To examine income-related inequalities in access to dental services from 1975 to 2018. In Norway, dental care services for adults are privately financed. This may lead to income-related inequalities in access. In the early 1970s, that is, at the beginning of the study period, there were marked inequalities in access to dental services according to personal income. However, from the beginning of the 1970s, there has been a large increase in gross national income per capita in Norway as a result of the growth of the oil and gas industry. This increase in income also meant that people with a low income in 1975 had a rise in their level of income. According to the law of diminishing utility, an increase in income leads to higher consumption of dental services for people with a low level of income compared to people with a high level of income. The study hypothesis is that the inequalities in access to dental services that existed in 1975 became less over time.


METHODS
Statistics Norway collected samples of cross-sectional health survey data for the following years: 1975, 1985, 1995, 2002, 2008, 2012 and 2018. For each sample, individuals 21 years and older were drawn randomly from the non-institutionalized adult population using a two-stage stratified cluster sample technique. Inequalities were measured using the concentration index. The dependent variable was the use of dental services during the last year, and the key independent variable was equivalized household income.


RESULTS
The concentration index for inequalities in use of dental services according to income decreased from 0.10 (95% CI = 0.09, 0.11) in 1975 to 0.04 (95% CI = 0.03, 0.05) in 2018. The decrease was particularly large from 2002 to 2012. This was a period with a large growth in gross national income.


CONCLUSION
People with a low income had a marked increase in their purchasing power from 1975 to 2018. This coincided with an increase in demand for dental care for this low-income group.