The Growth Of Monopoly Power

http://thesocietypages.org/socimages/2012/11/13/the-growth-of-monopoly-power/

Percentage of Sales for Four Largest Firms in Selected U.S. Retail Industries:

Industry (NAICS code)	1992	1997	2002	2007
Food & beverage stores (445)	15.4	18.3	28.2	27.7
Health & personal care stores (446)	24.7	39.1	45.7	54.4
General merchandise stores (452)	47.3	55.9	65.6	73.2
Supermarkets (44511)	18.0	20.8	32.5	32.0
Book stores (451211)	41.3	54.1	65.6	71.0
Computer & software stores (443120)	26.2	34.9	52.5	73.1