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Here is my working definition of a public health expert: someone who is constantly frustrated that people will not act on clear health advice in the interests of their own health.

From smoking to diabetes, from eating responsibly and exercising to practicing safe sex, from getting an annual flu shot to wearing face coverings in the time of coronavirus, the literature on public health is awash with tricks, nudges, and sometimes outright bribes to try and get people to take care of themselves. Some progress has been made, but the feeling is often one of disappointment that so many people aren’t following the advice.

Paradoxically, Covid-19 — the biggest public health and economic calamity in several generations — is showing that people can and will listen and act. We, the people, have done remarkably well around the world when it comes to following public health advice. This is in spite of the fact that several governments, including those of the U.S. and many states, have not supported the clear public health message that people need to make enormous changes to their behaviors to protect themselves and others.

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The evidence on this is actually very clear. While the pandemic has its ebbs and flows, a month or so after the first significant outbreak in a region (say, a city like New York or a state like Illinois) things stabilize. The virus doesn’t go away. Instead, the number of new infections is about the same from day to day. Epidemiologists refer to this situation as the reproduction rate of the virus going to 1, with every person who is infected spreading it to just one other person on average. (Getting the reproduction rate under 1 is the beginning of the road to stopping the pandemic.)

This stands in contrast to earlier predictions of a large outbreak as the virus spread quickly at much higher reproduction rates based on how easily the virus could jump from person to person. In the absence of behavioral change, an international team of researchers predicted that an infected person would infect two to three other people. That happened right at the beginning of the pandemic, but then it changed. Part of this was due to governments instituting lockdowns but, somewhat amazingly, people locked themselves down faster than governments acted.

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Perhaps the clearest study of this comes from University of Chicago economists Austan Goolsbee and Chad Syverson. Using cellphone data to track visits to 2.5 million businesses in the U.S. between March 2020 and May 2020, they examined counties in lockdown states that were next to counties in non-lockdown states. Although government lockdowns did reduce visits to businesses, 60% of the reduction would have happened even without them. In other words, people were acting. The converse happened as governments allowed reopening: People did not follow.

This pattern arose around the world. Very few people saw others falling sick or collapsing in the street, as happened during the 1918 flu pandemic. In fact, we saw nothing. Nothing but the news and information from experts. And that information spread quickly. Within a week or so, people knew what was happening even if they couldn’t see it happening. And they knew what the recommendations were even though officials were still not entirely certain about how Covid-19 was spreading.

It is tempting to think of the lockdown protests and mask boycotts and conclude that solid public health messages weren’t getting through. But the data show that those were the exceptions rather than the truth. Moreover, this information penetrated the far reaches of the planet. Even in places like Sweden and Brazil, which were perceived as not having strong government interventions against Covid-19, people found out about the risks quickly and acted to protect themselves.

Think, for example, of the mask misstep. Because public health officials were initially concerned about mask hoarding, they downplayed the need for masks. That was a mistake because mask use likely was the most effective tool in combating the spread of the novel coronavirus. Even so, more and more people began procuring masks or fashioning them themselves. And they wore them which, as these things go, was a huge behavioral change. They did to protect themselves but also to protect others. The information flowed. Only later did the official advice change and Americans were called upon to wear masks when in public.

The speed and reach of these personal changes in behavior strongly suggest the influence of one thing that we have today that wasn’t around in 1918 or even in the 1980s as HIV/AIDS began to spread: the internet. While there are genuine concerns about the internet as a conduit for misinformation, when it comes to public health messaging regarding the coronavirus pandemic, we owe it our gratitude. Covid-19 may go down in history as the internet’s first truly great informational triumph.

I realize this may be a controversial view. But there was no Walter Cronkite we all watched and trusted for our news. There were no public addresses from the president. There was just the decentralized mess and flow of information from the internet to our devices. When we look at 2020, it is reasonable to say that part of the system finally worked. When we look beyond 2020, we should ask what more it can do.

Joshua Gans is a professor of strategic management at the University of Toronto’s Rotman School of Management and author of “The Pandemic Information Gap: The Brutal Economics of Covid-19” (MIT Press, November 2020).

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