This 46-page Professional Opinion quantifies the block-by-block food access impact that the proposed Wal-Mart would have if it opens at that site. It also quantifies the impact of nearby grocers that have recently opened or closed. Retail agglomeration and new neighborhood market frameworks and measures are introduced, such as the Snowball Index and Snowball Effect, which explain why retail attracts retail and like attracts like. The work is a must-read for anyone interested in the complicated and interwoven dynamics of today’s commercial shopping districts.