2020 has been a rough year for many stock investors. For those who've concentrated on the Nasdaq 100 index of top stocks trading on the Nasdaq Stock Market, though, returns have been strong. As of July 6, the index was up 21% on the year and sitting at a new record.

Yet even though some huge, high-flying stocks have helped to lift the Nasdaq 100 higher, other companies in the index haven't made the grade. The values of some of the worst performers have actually fallen so far that they've been kicked out of the index -- among them, a couple of major U.S. airlines. Among the survivors, though, the following three stocks stand out for their declines so far this year.

MAR Chart

MAR data by YCharts.

Marriott, down 41%

It's no surprise to see Marriott International (NASDAQ:MAR) leading the list of losing stocks in the Nasdaq 100. The travel industry has taken a huge hit from the coronavirus pandemic, and Marriott's leading position in the hotel business has exposed it to the impact of huge reductions in travel volume and fewer people seeking accommodations on the road.

Multistory hotel with Marriott logo on the top floor, with nearby surroundings also shown.

Image source: Marriott.

Believe it or not, a 41% decline is actually quite a bit better than Marriott's worst level during the first half of the year. The hotelier's first-quarter results were scary, with earnings falling more than 90% year over year and revenue per available room (RevPAR) plunging 22.5%. Things were even worse in April, with RevPAR down 90% from April 2019. Yet now, hotels are starting to reopen, and investors hope that Marriott will get its upward momentum back. A lot depends on what happens next with the pandemic. With outbreaks  intensifying in many states and with the U.S. having already set two new records for the number of daily COVID-19 diagnoses in July, it's clear the headwinds for Marriott are far from abating.

Western Digital, down 32%

Western Digital's (NASDAQ:WDC) presence on this list might feel more counter-intuitive. Many tech companies have posted sharp gains in 2020, especially those that stand to cash in on the move toward greater digitalization. With cloud data centers becoming increasingly vital, you might think that Western Digital would have a natural market for its data storage solutions. Indeed, its fiscal third-quarter numbers included a 14% rise in revenue, powered by its strength in data center products and client devices.

There were a couple of problems, though. First, Western Digital had to deal with major disruptions to its supply chain this year. That boosted its costs, and even though adjusted earnings were substantially higher than they were a year ago, they nevertheless left investors wanting more. Also, the hard drive company suspended its dividend to conserve cash. That removed what had been an extremely attractive dividend yield that had kept many investors interested in the stock.

New CEO David Goeckeler will have to keep transforming Western Digital away from its outdated hard drive emphasis and toward a focus on flash memory and solid-state drive solutions. That'll be a long road, but that's what it'll take to pull Western Digital stock out of its tailspin.

NetApp, down 28%

Like Western Digital, NetApp (NASDAQ:NTAP) should also, in theory, have held up better during the coronavirus pandemic. In its fiscal fourth-quarter results in late May, the company reported that its cloud data services revenue had more than doubled from year-ago levels. Yet investors focused on falling sales and profits that stemmed in part from the difficulties of navigating the pandemic.

In early June, NetApp doubled down on the cloud computing space with the strategic acquisition of cloud infrastructure management specialist Spot. The move should bolster the combined companies' presence in the cloud, but investors aren't certain whether the acquisition will be enough to move the needle at NetApp. With other providers pulling ahead, it's unclear whether it can close the gap.

Looking for the best stocks

When there are plenty of fast-growing companies for investors to choose from, it's hard to have much patience for weak performers like these. NetApp, Western Digital, and Marriott have room to recover, but there are more promising businesses elsewhere that have greater potential to deliver strong returns over time.