Shares in Hong Kong-listed airline Cathay Pacific have dropped to a nine-year low, down from HK$12.22 (US$1.56/£1.20) at the start of the year to HK$9.96 ($US1.27/£0.98). The reason? A massive data breach that has affected 9.4 million customers and eroded confidence in the company.
How safe is your data? Read about the scariest online scams and hacks of 2018.
Harley-Davidson is having a horrendous year with its share price trading near a seven-year low, down from $52.06 (£39.97) at the beginning of January to $38.49 (£29.55). Trump administration tariffs have pushed up costs, and moved some production overseas, and sales have slipped as the iconic motorcycle manufacturer struggles to attract younger customers.
Discover which other companies are struggling under the Trump administration.
Down from €101.36 (US$115.97/£89.01) at the start of 2018 to €67.71 (US$77.47/£59.46), shares in German pharmaceuticals giant Bayer have been falling since August when a Californian jury awarded $289 million (£222m) to former school groundskeeper Dewayne Johnson, who claimed that glyphosate, the key ingredient in Roundup weedkiller, caused his terminal cancer. Bayer acquired Monsanto, the controversial US firm that makes Roundup, earlier this year and now faces a tidal wave of related lawsuits.
The world's largest PR and ad agency, Britain's WPP has seen its share price plunge this year, down from £13.36 at the start of 2018 to £8.88. Several factors are behind the fall, including the abrupt departure of company founder and CEO Martin Sorrell (pictured) in April, the weak pound and a slowdown in business in the US.
Now discover the world's most valuable companies.
Shares in Massachusetts-based Merrimack Pharmaceuticals have dropped to a near-record low of $3.95 (£3.03), down from $10.65 (£8.18) at the beginning of the year. The clinical-stage oncology company recently announced it had canceled a phase two trial of a combination drug treatment for lung cancer, which explains the plunge.
See which American companies rule the world at the moment.