Willis Tower new competition by retailing giants such as Kmart, Kohl's, and Walmart. The fortunes of Sears & Roebuck declined in the 1970s as the company lost market share; its management grew more cautious. Nor did the Sears Tower draw as many tenants as Sears had hoped. The tower stood half-vacant for a decade as a surplus of office space was erected in Chicago in the 1980s. In 1990, the law firm of Keck, Mahin & Cate decided to move out of its space in the Sears Tower and into a development that would become 77 West Wacker Drive, rebuffing Sears' attempts
Merchandise Building forces with Sears-Roebuck & Co. of Chicago in forming a 50/50 ownership in a new company, Simpsons-Sears Limited. The new firm took control of Simpson's catalogue and mail-order business and would open new Sears-style department stores in markets not already served by Simpsons. It was seen as better suited to take on competition with the strong T. Eaton Co. catalogue business and to use Sears marketing principles to expand into smaller Canadian rural and suburban markets. The Toronto Mail Order Building complex - which eventually came to be known by the less cumbersome name of "the Mutual Street Building", continued