In the long history of poor management decisions made at major American companies, only a few proved to be fatal. It is hard to ruin a company with a single decision. That is especially true when the company has the advantages of huge market share, large and rising revenue, and a history of success. But not all bad decisions are created equal. 24/7 Wall St. set out to identify the worst business decisions of all time. These decisions cost these companies billions of dollars and, eventually, their independence.

Bad business decisions result in financial loss. The worst business decisions lose companies billions in revenue. Our editors relied on Fortune magazine’s annual list of the largest 500 companies ranked by revenue to identify the companies that were the biggest in America and, as a result, capable of losing the most money.

To make the initial cut, companies had to be on the Fortune 100 list for at least 10 consecutive years and then drop off the top 100 ranking for good. We then looked for the companies that made a single identifiable decision that cost them significant revenue and ultimately led to their decline. Based on this cut, 24/7 Wall St. identified the eight companies that suffered from the worst business decisions of all time.

Inclusion at the top of the Fortune 500 is hard to get, but, once won, it is also hard to lose. Nearly three-quarters of 2012’s 100 largest companies have been in the top 100 for at least a decade. This includes 23 that have been there for a quarter century, as well as 13 companies that have been on the list since it debuted in 1955. Even if a company falls out of the top 100, it usually remains a large company for a long time. Seventy companies from the original Fortune 100 are still somewhere on the Fortune 500 list.

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