Reilly's Law remained an interesting hypothesis for more than a decade and, as late as 1944, the editor of The Journal of Marketing, which became a key academic testing ground for Reilly's Law, wrote that there is a real need for inductive studies of consumer buying habits" (quoted in Bennett, 1944, p.
Converse (1943; 1946; 1948), a professor of business at the University of Illinois, who examined retail customer movement between several communities in Illinois and established the usefulness of Reilly's Law for defining retail trade areas across a much larger geographic area.
60) findings reinforced previous studies and again found that Reilly's law of retail gravitation provides a remarkably accurate delineation of the Charlotte retail trading area." However, Douglas's empirical findings also suggested a slight modification to Strohkarck's and Phelps' concept of concentric market areas.
The results of these studies were so consistent and so reliable that nearly three decades after the publication of Reilly's Law of Retail Gravity (1931), Robert Ferber (1958, 302) was able to declare that: "The two variables included in Reilly's Law and in subsequent formulations--population, and distance--account for almost all the variations in sales between cities."
Indeed, after three decades of testing Reilly's Law, Allen F.
Scholars, retail executives, real estate investors, and urban planners enthusiastically embraced Reilly's Law of Retail Gravitation as an iron law of retail trade distribution, but at the same time a number of methodological amplifications were introduced in the 1960s and 1970s which culminated in the introduction of the "Huff model" (Applebaum, 1965, p.
303) consumer behavior research, which was based on Reilly's Law had found that income is a major factor influencing variations in per capita retail sales between cities for most categories of sales." Similarly, Bucklin (1967b, p.
84) identified another significant limitation to the application of Reilly's Law, which is that the calculation of breaking points to delimit a retail trade area conveys an impression that a trading area is a fixed boundary circumscribing the market potential of a retail facility, when in fact there is an exponential distance decay factor of declining retail attraction within the trade area, as well as interpenetration and overlap between designated market areas." This problem had been identified earlier in the development of gravity modeling by scholars, such as Edna Douglas, who had mapped trade areas based on actual consumer origins, rather than distance postulates.
The Huff model, which was first articulated in two articles published I in 1963 and 1964, incorporated these four modifications to Reilly's Law to construct an alternative model of retail gravitation based on consumer behavior theory and goods theory, rather than central place theory.