Access or adaptation? A meta-analysis of surveys of problem gambling prevalence in Australia and New Zealand with respect to concentration of electronic gaming machines

Abstract

It is widely believed that greater availability of electronic gaming machines (EGMs) has led to increases in problem gambling prevalence and related harms. It has also been proposed that individuals and populations adapt to exposure over time and that prevalence rates plateau or decline, even in the face of increasing availability. This study examines both hypotheses using a combined data set of 34 problem gambling surveys conducted in Australia and New Zealand since 1991. Strong statistically meaningful relationships were found for an increase in prevalence with increasing per capita density of EGMs, consistent with the access hypothesis and supported by no evidence of plateauing of prevalence with increasing density of EGMs. A decrease in prevalence over time with availability held constant is also evident, partially consistent with adaptation. It is likely that both forces are at work simultaneously, with implications for appropriate policy responses to gambling harm minimisation.

Keywords:

• electronic gaming machines
• prevalence
• policy
• problem gambling
• social costs

Notes

1. For linear regression analysis, R ² is defined as the coefficient of determination and interpreted as the percentage of the variation in y about its mean that is explained by the regression model. The p value is a report of a hypothesis test. Where the p value is smaller than the chosen value of α (α being the probability of rejecting a true hypothesis), then the test procedure leads to rejection of the null hypothesis. (For a discussion, see Hill et al., 2001, pp. 124, 104.)

2. This is not to say that the data refuted the hypotheses, but rather that there was insufficient information in the data to accept the conclusions at an appropriate level of confidence.

3. The various sources are referenced and discussed below. PGSI scores have been adjusted to SOGS5 as discussed below.

4. Regardless of the probability distribution of the population being sampled, for sufficiently large samples the central limits theory suggests that the sampling distribution will approximate a normal distribution. The judgement is as to what comprises sufficiently large.

5. Collinearity is a technical problem in linear regression analysis whereby a model that includes two independent variables that are themselves strongly correlated with each other will return anomalous results. In the extreme where the two variables are perfectly correlated, the method of analysis will fail.

6. The method of least squares assumes a uniform distribution of variation across the model. Where variance decreases or increases systematically with an independent variable anomalous results may be obtained. Where evidence is found for heteroskedasticity, the usual approach is to use a transformation such that the distribution of variance is then constant.

7. That is to say, there is about a one in four chance that the rate of problem gambling prevalence increases with increasing density rather than decreasing and plateauing then reducing.

8. Density is only one aspect of access, however the high R ² value suggests it is an important aspect with respect to prevalence of problem gambling.

9. The latter findings relate to expenditure but are relevant insofar as expenditure is a proxy for problem gambling.