Leverage is a by product of efficiency, NOT separable in business. I agree Wal Mart, on occasion does bully (so to speak) its suppliers. However Wal Mat has made many small companies, very large. Three or four times a years they hold meeting for small companies (from around the world) in Arkansas. Of the thousand (thousands more refused attendance) or so, in any one year that attend, 20-50 may be chosen to place products in some to all their outlets. Many do so, at a loss to expenses, considering the process to name recognition which would cost much more otherwise. There is no bill board sign anywhere, where more people will see your product on a daily basis. To top this off, if your product or service is successful (sells) WM will not pull your product. They do have a THREE PRICE system, based on locations and areas where some products do good opposed to others, work with suppliers and in many cases buy out the company.
Actually Wal Mart, has increased labor cost in every town it enters. Mom and Pops, as a rule pay the least wages, never with any form of benefit package. Its been a good many years since I checked this out, but think by 2000, there were some 3-4000 people who had retired from WM millionaires, from Stock in their retirement programs.
WM is not the only story on these issues. Big business has done no less in many fields and I won't bother you with statistics on what these companies have done for towns, counties or states through taxes of civic involvement.