Apple (AAPL 0.42%) shares soared during the first six months of 2015, rising around 20% from the beginning of the year to the end of May. But over the past seven months investors have lost interest. The iPhone maker is poised to close the year roughly unchanged.

What fueled Apple's decline in the second half? A series of unfortunate events, including a disappointing earnings report, fears about the Chinese economy, and doubts about the long-term success of the iPhone business all played parts. Let's take a look at some of the most significant negative headlines that weighed on Apple shareholders in 2015.

Mixed reviews for the Apple Watch
In April, Apple launched its first major new product category in several years. The Apple Watch is Apple's first wearable, and while it wasn't the world's first smartwatch, there's nothing else quite like it. The Apple Watch is a fitness device, fashion statement, and iPhone accessory rolled into one.

It would be unfair to say critics trashed the device, but most were unsupportive. The Verge awarded it a modest 7 out of 10, citing performance issues. CNet found fault with the battery life and characterized the interface as "confusing". The Wall Street Journal's Joanna Stern wrote that most consumers would be better off waiting for a better model.

That lukewarm reception didn't seem to weigh on Apple's share price in April, but it may have limited its upside. The Apple Watch isn't a dud -- research firm IDC reported that Apple shipped 3.6 million Apple Watches in the second quarter -- but it wasn't the wearable revolution that many hoped for, at least not in its debut form.

A disappointing earnings report
Apple turned in two strong earnings reports to start the year, posting record earnings in both January and April. But in July it stumbled. During the company's fiscal third quarter, earnings and revenue exceeded analyst expectations, but it sold fewer iPhones than anticipated. The iPhone business grew, but not to the extent that many had hoped. The 47.5 million iPhones Apple sold represented annual growth of 35%, but some analysts had been expecting unit shipments to top 50 million.

Cook reaches out to Cramer as Chinese fears take a toll
China is increasingly important to Apple. Last quarter, it generated about one-quarter of the company's revenue, and it was Apple's fastest-growing segment, as sales nearly doubled on an annual basis. Given the large number of Chinese consumers, that may be a net positive overall, but it worked to the company's detriment in August.

The Chinese stock market was especially volatile for most of the year, particularly in the summer. Chinese shares plunged upward of 30% at one point, prompting regulators to halt vast swaths of the market during the summer months. Investors reacted by selling Apple shares, betting that a slowing Chinese economy would weigh on the company's sales. In August, CEO Tim Cook sent an email to CNBC's Jim Cramer, defending the company's Chinese business and its performance. That helped shares recover somewhat, but the stock has remained subdued ever since.

Analysts warn about the iPhone in 2016
More recently, fears of weak demand for Apple's latest iPhone models -- the iPhone 6s and iPhone 6s Plus -- have served to keep a lid on Apple stock. As early as October, analysts had warned that demand for the iPhone 6's successor appeared far weaker than demand for its predecessor. The smartphone market is showing signs of saturation, and while the iPhone 6s offers a number of improvements, it's not a radical overhaul like last year's iPhone 6.

Several firms, including KGI Securities, Pacific Crest, and Morgan Stanley, now expect iPhone sales to contract in 2016. If so, it will represent the first decline for the business since the original iPhone made its debut in 2007.