In Chapter 2 we described the difficulties involved in defining and measuring pathological gambling using various assessment instruments. Here it is important to note that comparing and interpreting prevalence findings is problematic when different studies use different screening and/or diagnostic instruments or criterion levels to measure differing levels of intemperate gambling and associated problems. Unfortunately, such differences are common in the research literature on pathological and problem gambling (Volberg, 1998b), which creates problems in estimating prevalence rates in the United States.
Another important limitation of the available prevalence research pertains to the different facets of the concept of prevalence. A prevalence estimate requires specification of the population or geographical area represented and the time frame over which prevalence is defined (Walker and Dickerson, 1996). Most of the prevalence research on pathological and problem gambling is specific about the population or area represented, but the time frames within which gambling behavior is assessed vary widely. This variation is troublesome because the information of greatest policy relevance is generally the prevalence of current pathological or problem gambling, that is, estimates over a relatively recent but behaviorally representative time frame (e.g., the past year). The time frame most common in available research, however, is lifetime. Thus, many of those who are counted in prevalence research as being pathological or problem gamblers may have met screening or diagnostic criteria at some point during their lives, but did not manifest gambling problems at the time of the study.
Measuring pathological and problem gambling also requires distinguishing incidence from prevalence: incidence is the number of new cases arising in a given time period, and prevalence is the average total number of cases during a given time period, factoring in new cases and deleting cases representing cures deaths. Incidence is especially pertinent to policy questions involving the effects of increased gambling opportunities and changes in technology, industry practices, and regulation. There is almost no research that examines the incidence of pathological or problem gambling cases over a representative, recent time