In April, CDC recommended that all Americans wear a face mask or covering in public places where practicing social distancing would be difficult, yet a sizable number of Americans still aren't wearing masks in public, surveys suggest.

Just how effective are masks at stopping coronavirus? Here's what new research says.

How many Americans don't wear masks?

According to a report from CDC, a majority of Americans support wearing face masks or coverings in public to help combat the new coronavirus' spread. From May 5 to May 12, CDC surveyed 4,042 adults throughout the country and found that 60.3% of respondents said they always wore a mask when out in public, while 13.8% say they often wore a mask in public. However, 17.1% of respondents said they either rarely or never wore a mask in public.

CDC found that women were more likely than men to say they always wore a mask in public. Similarly, a separate study based on the results of surveys conducted among 2,459 U.S. adults on April 28 and May 4 found that men were less likely to believe they'd be seriously affected by Covid-19, the disease caused by the new coronavirus, and were more likely to view wearing masks as "a sign of weakness."

Meanwhile, according to a HuffPost/YouGov poll conducted from May 14 to May 16 that surveyed 1,000 adult Americans, 62% of respondents said the decision to wear a mask is more about public health than personal choice, and 69% said it's respectful to wear a mask in public. In that poll, about two-thirds of respondents said they always or mostly wore a face mask in public and near other people, while 23% said they wore a mask either once in a while or not at all.

Why some Americans don't wear masks

According to David Abrams, a professor of social and behavioral sciences at NYU School of Global Public Health, humans tend to long for a sense of belonging in uncertain times—and that applies to people on both sides of the political spectrum. People who don't wear masks may see it as a sign of solidarity, as if they are together making a stand against authority, while those who do wear masks likely see it "as an act of altruism and a way of helping each other out," Abrams said.

The same dynamic applies to people who have lost a loved one to Covid-19, Abrams said. They are more likely to wear a mask in part because "[t]hinking about real people and personalizing coronavirus gets at that emotion of altruism and nurturance," he said, adding, "You side with the tribe that wears masks and you go, 'Oh, I want to be part of that.'"

To get a man-on-the-street perspective of these decisions, Steve Lopez, a columnist for the Los Angeles Times, walked through downtown Glendora, California, at lunchtime on Tuesday to ask people about their thoughts on wearing masks in public. Lopez estimated that he saw "one-third with [masks], two-thirds without."

One of the people Lopez spoke with—a 77-year-old man who was not wearing a mask—said people wearing masks were "probably driven by political scare tactics," adding that he didn't know anyone who had contracted the new coronavirus. The man said he believed that if case counts of the virus are increasing, it's likely due to more diagnostic testing rather than a surge in the novel coronavirus' spread.

Lopez also came across a woman named Robin who, alongside her daughter Natasha, were not wearing masks. Robin said she prefers to breathe in fresh air on a nice day, and she and Natasha wear masks when they're in stores.

However, neither Natasha nor her daughter were fully convinced on the efficacy of wearing masks, Lopez reported, with Natasha saying CDC had contradicted itself on the practice.

Separately, a man named Jon who spoke with Lopez said he goes to a bar every night and no one in the bar wears a mask. Jon, who told Lopez that he lost his job because of America's coronavirus epidemic, said he doesn't have a problem with people at the bar going without masks. While Jon acknowledged that the virus can be deadly, he wondered why Los Angeles County was more focused on newly confirmed cases of the virus, as opposed to how many people had recovered from infection

What the evidence says on face masks

For their part, public health experts say that—while there remains uncertainty about just how effectively face masks or coverings can prevent coronavirus transmission—the evidence overall indicates they can play an important role in limiting the epidemic's spread.

For example, a review of 172 observational studies published earlier this month in The Lancet concluded that wearing face masks or coverings can help curb the risk of coronavirus infection and transmission. Holger Schünemann, a co-author of the review and an epidemiologist and physician at McMaster University, said the review indicated that "[i]n multiple ways … the use of masks is highly protective in health care and community settings."

Jeffrey Shaman, an epidemiologist at Columbia University, said, "Anecdotally, it appears that face-mask use is an important control against multiple modes of [new coronavirus] transmission." He added, "[S]tudies support this anecdotal observation and provide some quantification of the effects of face masks" (Buchwald, MarketWatch, 6/16; Edwards-Levy, HuffPost, 5/20; Lopez, Los Angeles Times, 6/17; CDC Morbidity and Mortality Weekly Report, 6/12; Capraro/Barcelo, PsyArXiv Preprints, 5/16; HuffPost/YouGov poll, accessed 6/17).