It's been a banner year for the stock market. However, not every stock has been a winner as some sectors performed better than others. Tech and utilities soared, while others like real estate and healthcare underperformed.

So what are the five worst performers on the Dow Jones Industrial Average (^DJI -0.77%) list of blue chip stocks? Let's take a look.

1. Boeing (down 36.5%)

Boeing (BA 0.19%) has had a rough year. It started early as the stock price fell after the door panel on a Boeing jet flown by Alaska Airlines popped off mid-flight. Follow-up investigations revealed a workplace culture where quality controls became overly lax. Boeing brought in a new CEO, but a full-fledged turnaround could take years.

2. Nike (down 27.5%)

Nike (NKE -0.68%) struggled this year as missteps under former CEO John Donahoe (also ousted this year) led to declining sales and profits and market share losses to upstart competitors like On Holding and Deckers' Hoka brand. Nike was also criticized for moving away from brand marketing and wholesale relationships with chains like Foot Locker. It's expected to change strategy under new CEO and company veteran Elliott Hill.

3. Merck (down 8.5%)

Merck (MRK -0.17%) is one of several pharmaceutical stocks that underperformed this year. The company struggled to find growth beyond Keytruda, a cancer drug, as franchises like HPV vaccine Gardasil and diabetes drug Januvia declined due to Gardasil's weakness in China and competition for Januvia. Keytruda now makes up nearly half of its revenue, though the headwinds against other drugs have eaten into profits.

4. Johnson & Johnson (down 6.3%)

Johnson & Johnson (JNJ -0.36%) is also down this year as it's faced headwinds associated with lawsuits around its talcum-based products, and profits have declined due to legal costs and increased research and development (R&D) expenses.

5. Amgen (down 4.8%)

Like other healthcare stocks, Amgen (AMGN -0.20%) missed out on the cyclical tailwinds that lifted the broad market, and it's faced challenges with MariTide, a weight loss drug that could be linked to bone mineral density loss. Revenue from oncology treatments and established products like Enbrel are also down.