One of the factors that usually plays a part in an economic impact study like that used to promote the Downtown Wichita arena is the “multiplier,” which accounts for the fact that money spent once is spent again, and maybe yet again.
To quote from “Economic Impact Multipliers for Kansas” published in “Kansas Business Review” Vol 12, No. 3, Spring 1989, and available at http://www.ku.edu/pri/publicat/multipliers/multipliers.htm:
It sometimes seems that the bigger a multiplier is, the more often it is quoted. (1) In any case, some distinctly one-sided political and economic motives encourage the propagation of exaggerated multipliers.
In particular, economic multipliers are used to justify public concessions to private industry. Such assistance for business may include land acquisition, new roads and sewers, job training programs, subsidized loans, and tax incentives.(2) The extent of public concessions is determined through bargaining between government and industry, and in the course of the bargaining those who stand to gain most from the new enterprise have a natural tendency to inflate the relevant multipliers.(3)
The inflation of multipliers may stem less from venality than from an innate optimism, which seems to be necessary in the risky business of development. Since multipliers are costly to measure, of uncertain accuracy, varied in their meanings, and multifarious in their origins, a convenient range of multiplier values is always available; discriminating users are free to choose the best values for their purposes.