The drop in oil prices last year might have been good news for U.S. motorists, but it wreaked havoc for oil drilling companies. Oil and natural resource companies snagged five slots on the list of the 15 companies that lost the most money in 2014, the largest industry contingent on the list. Pharmaceutical companies were a close second with four companies among the top 15, and the tech industry was represented with three companies. Giant e-retailer Amazon.com made the list as well.

24/7 Wall St. reviewed the 15 publicly traded companies with the largest losses in 2014. The list was led by oil and gas producer Apache Corp., which reported a staggering $5.4 billion loss. Together, the 15 companies lost $21.7 billion in 2014 on collective revenues of $267.5 billion.

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Of the 15 companies recording the greatest losses, only two — Target and Amazon.com — were within the top 40 publicly traded companies in the country by revenue. Amazon.com ranked 26th out of the the S&P 500 companies with just under $89 billion in revenue, and Target ranked 37th with nearly $73 billion in revenue.

Losses among energy companies were largely due to writedowns resulting from the plunge in oil prices. Oil drilling and exploration companies were forced to write down the goodwill on their balance sheets because the drop in oil prices made drilling new wells uneconomical and decreased the value of their oil reserves.

While the colossal losses reported were certainly bad signs, for some of these companies, including some of the energy companies, this was not necessarily the case. In fact, the recorded losses do not necessarily signal failing businesses, as 11 of the 15 companies reviewed experienced an increase in revenues from 2013 to 2014.

In some instances losses resulted from one-time events such as costs associated with acquisitions or with eliminating a money-losing operation, actions which could turn into profits in future years. In still other cases, large-scale mishaps accounted for the bulk of losses.

Five of the companies losing the most money invested substantially acquiring other businesses in 2014. Pharmaceutical company Actavis, plc, for example, lost $1.6 billion in 2014, some of which was attributable to costs associated with its acquisition of Allergan, another in its series of strategic acquisitions.

Target Corp., which reported losing $1.64 billion in 2014, took a $4.1 billion charge when it closed its money-losing operation in Canada.

Transocean was found to be 30% at fault for the Deepwater Horizon disaster in the Gulf of Mexico in April 2010, which killed 11 workers and caused one of the largest oil spills ever. This accounted for the bulk of the company’s reported loss. Transocean, nonetheless, increased its dividends for shareholders in 2014. Five of the companies losing the most money increased their dividends from 2013 to 2014.

While the pharmaceutical companies overall took writedowns either to cover acquisition or similar transaction expenses, in one instance the loss followed complications with a particular product. In the fourth quarter of last year Vertex Pharmaceuticals withdrew Incivek from the U.S. market after patients reported serious skin reactions.

To identify the 15 publically-traded companies recording the largest losses in 2014, 24/7 Wall St. reviewed net income losses in the most recent fiscal years among companies in the Standard & Poor’s 500. When available, the net income attributable to shareholders was used. We also reviewed company websites and financial documents submitted to the Securities and Exchange Commission. One-year stock price change was measured over the period between May 1, 2014 and April 30, 2015 from Google Finance.

These are the 15 companies which lost the most money in 2014.