Does a reduction in the overall amount of gambling imply a reduction at all levels of gambling?

The frequencies of slot machine gambling decreased in Norway after a major regulation in the slot machine market in 2006. This study addressed whether a change in population gambling frequency mean is accompanied by a systematic displacement at all levels of gambling frequency among adolescents, across different population samples, and over time in the same population. Data were collected in two cross-sectional school surveys among 13–19 year olds in Norway in 2005 and 2006. Net samples comprised 21,202 and 20,642 students, respectively. The students reported annual gambling frequency for six games for money, and a variable for total gambling frequency was analyzed. A strong regularity in the distribution of gambling behavior was observed and gambling at all levels, from light and moderate to frequent and excessive gambling, varied systematically with mean gambling frequency. Thus, a change in the population mean was accompanied by a systematic displacement at all levels of gambling behavior and not only at high to excessive levels of gambling. The findings are in line with those reported in other health areas and relevant to a public health perspective on problem gambling, suggesting that prevention strategies aimed at the total population of gamblers may also affect excessive gambling.