Geographical coherence may be defined as the degree to which the behaviour of a time series in one geographical area corresponds with the time series behaviour in another. This paper illustrates the concept using the epidemiological time series of reported monthly measles morbidity for the states of the United States for the 27 years from January 1962 to December 1988. Over this period, as measles morbidity has declined in response to vaccination campaigns, and as the seasonal peaking of the disease in late spring has become less pronounced, the geographical coherence has altered at the national, divisional, regional and state levels. There was a steady decline in coherence from 1962 to 1980. In 1981, a dramatic reduction occurred, but there has been some recovery since. The implications for spatial forecasting models of these reducing levels of coherence are discussed.

Purpose The cost of course materials to the individual student has increased over the past decade, contributing to educational inequity. Open educational resources (OERs) may be a solution and research validates their positive impact on student success outcomes (Colvard et al., 2018; Feldstein et al., 2012). Few studies, however, examine the role that library collections play in addressing course materials cost and student success. This paper aims to investigate whether materials costs are a significant factor in course pass rate and whether the library has a positive impact on pass rates. Design/methodology/approach Using required texts listed in syllabi for select undergraduate courses at California State University, Northridge (CSUN), the authors compare course materials costs for each course to the pass rate. The authors then measure the impact of course materials cost on the achievement gap between Pell Grant eligible and non-eligible students. Findings This study confirms previous research indicating that reduced course materials costs have a measurable impact on student success, in that the total minimum cost of required materials has a statistically significant effect on the percentage of students who pass a course. However, course reserves slightly increase the disparity between high-income and low-income students, suggesting that course reserves are a less effective way of supporting the latter compared to OERs. Originality/value This study is unique in examining the effect of the cost of course materials on students, regardless of the source of cost reductions. Most literature focuses on the qualitative efficacy of OERs instead of measured impact or the relationship between the cost of course materials and student success. The authors investigate the connection between OERs, library engagement and student success.