Lockdowns save lives. The evidence is clear around the world.

• Overwhelming evidence suggests that lockdowns help contain coronavirus outbreaks and prevent additional deaths.
• Italy's lockdown prevented around 200,000 hospitalizations, according to a recent study.
• Another study found that Wuhan's restrictions prevented tens of thousands of infections throughout the Hubei province.
• While it's possible to reduce transmission through social distancing alone, lockdowns ensure that citizens abide by these guidelines.
• Visit Business Insider's homepage for more stories.

More than a third of the global population is under some restriction on movement related to the coronavirus pandemic. But after several weeks of lockdown measures, small groups have begun to protest and entrepreneurs like Elon Musk have argued that countries should open back up.

"Give people their freedom back!" Musk tweeted on Wednesday, linking to a Wall Street Journal op-ed from TJ Rodgers, the founder of manufacturing company Cypress Semiconductor.

Rodgers recently outlined two arguments for why US lockdowns were a mistake: The first is that his own analysis found a minimal correlation between states that closed businesses early and their overall death count (adjusted for population size). The second is that Sweden — where many schools and businesses remain open — has a lower death rate than some European nations that imposed full lockdowns, like Italy, Spain, and the UK.

But overwhelmingly, evidence suggests that lockdowns help contain outbreaks and save lives.

China, Germany, and Spain all saw their number of daily infections drop off after lockdowns were instated.

In Italy, a team of researchers recently simulated what could have happened if the country's restrictions had been relaxed in March — or not imposed at all. The results showed that the country's lockdown prevented around 200,000 hospitalizations between February 21 (when Italy's first case was reported) and March 25. It also reduced transmission of the virus in Italy by around 45%, according to the study.

Another group of scientists found that Chinese cities that implemented restrictions before they discovered any COVID-19 cases saw one-third fewer cases during their first week of infections than cities with delayed responses to the outbreak.

"Social distancing provided by the lockdowns has clearly slowed the spread of the virus," Jeffrey Morris, director of the biostatistics division at the University of Pennsylvania, told Business Insider.

Morris estimated that most places in the US have reduced their normal activity levels by 70% due to lockdowns and social distancing. That means fewer opportunities for the spread of infection.

Cities that locked down in China and Italy saw fewer infections

Now that China's outbreak appears to be contained and Italy's seems to be winding down, data from both countries offer a retrospective on why lockdowns work.

A recent study of restrictions in Wuhan, China — where the virus was first identified — found that the city's lockdown on January 23 prevented tens of thousands of infections throughout the Hubei province. Without the lockdown, cases in Hubei would have been 65% higher, the study found. International researchers also recently determined that overall social distancing in China reduced the number of daily interactions by at least sevenfold, thereby lowering transmission.

In Italy, towns with lockdown measures also seemed to fare better than those without.

The nation reported its first coronavirus case — a man in Lodi, a province in the northern region of Lombardy — on February 21. Epidemiologists have determined, however, that the virus was likely circulating in the region as early as January.

Lodi went into lockdown on February 23. That same day, Bergamo, another Lombardy province that wasn't under lockdown, reported its first case.

But it took until March 8 for Bergamo to shut down, despite a recommendation from Italy's Superior Institute of Health for the province to be sealed off on March 2. By that time, the virus was spreading rapidly throughout the area.

The number of overall cases in Bergamo tripled from March 9 to March 16, according to a WSJ analysis. Meanwhile, the number of cases in Lodi rose by less than 50%. By March 16, Bergamo reported more than 3,700 coronavirus cases compared to less than 1,400 in Lodi.

"Clearly, with the benefit of hindsight, we should have done a total shutdown in Lombardy, everyone at home and no one moves," Andrea Crisanti, a microbiology professor at the University of Padua, told ABC News. "Probably for political reasons, it wasn't done."

By April 6, Bergamo represented around two-thirds of Italy's total cases. Tens of thousands of people have signed a petition demanding to know why the province wasn't sealed off.

Sweden's lax approach might not work in other countries

Whereas many countries closed schools and non-essential businesses in response to the pandemic, Sweden has opted to keep its primary schools, restaurants, bars, and gyms open.

The decision has incited criticism among public-health authorities who fear that the lack of restrictions will result in unnecessary deaths. In a joint article in the Swedish daily newspaper Dagens Nyheter, Bo Lundback, a professor of epidemiology at the University of Gothenburg, called for "rapid and radical measures" to contain Sweden's outbreak.

As of writing, the country has nearly 12 times the number of COVID-19-related deaths than two other Nordic nations that imposed lockdowns: Finland and Sweden. Charts released by Pantheon Macroeconomics also show that Sweden's number of new coronavirus cases is still on the rise.

A recent Politico analysis also found that Sweden has a lower doubling time — the number of days it takes for coronavirus cases to double — compared to many other European countries, including France, Germany, Austria, and Spain. When the doubling time is low, the virus spreads more quickly.

As of Monday, the number of coronavirus cases in Sweden was doubling every 18 days compared to every 53 days in Spain and Germany and every 151 days in Austria. That means Sweden's outbreak could wind up being much more fatal than its death rate currently suggests.

What's more, the country hasn't completely bypassed restrictive measures. High schools and universities are closed and Sweden has banned gatherings of more than 50 people. Residents are being asked to social distance in public and stay home if they're sick or elderly.

The strategy assumes that citizens will exercise personal responsibility — something that has been harder to enforce in other, larger countries.

In Italy, by contrast hundreds of thousands of citizens received police citations for ignoring the country's lockdown restrictions in the days after they went into effect. People continued to host events, break curfew, and wander outside, CNN reported. In Australia, similarly, Bondi Beach was packed with visitors in March despite guidelines to social distance, forcing the government to close the beach. And in London, people continued to crowd the subway even after train access was limited to essential workers.

"While Sweden never instituted total lockdowns, many people followed the same social-distancing guidelines people during lockdowns were following," Morris said. "If Sweden or any other place tried to deny the seriousness of COVID-19 and lived life 'as usual,' it is likely that incidence and death rates would have skyrocketed."

There are different ways to enforce a lockdown, but social distancing is key

Rodgers's analysis suggested that shutting a state down quickly didn't save many lives in the US, but Morris pointed out several issues with the argument.

For one thing, Morris said, there's no consistent definition of a lockdown across all 50 states. Some states have allowed restaurants to stay open, while others issued only partial stay-at-home orders. New York is also an outlier, since it represents more than a third of the nation's coronavirus deaths — far more than any other individual state. That means it can skew the results.

"I find the analysis they did to be simplistic and clearly not the best way to answer the question," Morris said. Additional factors like population density could also influence a state's death rates, he added.

In an op-ed for the Philadelphia Inquirer, Morris suggested that restrictive measures could be tailored to communities based on their density and demographics. Areas with higher density may require stricter lockdowns than most, he wrote, since they create more opportunities for people to interact. Places with a higher proportion of elderly residents — who are especially vulnerable to the virus — might also benefit from more stringent shutdowns, too.

Countries and cities can also adjust the severity of their lockdowns depending on the state of the outbreak. Wuhan, for instance, resumed transportation into and out of the city after 76 days, but schools still remain closed and local officials are asking people to stay home as much as possible.

A recent NBER paper found that the optimal lockdown policy involves a severe lockdown two weeks after an outbreak is detected, which is then gradually withdrawn after three months.

"Clearly we need for society to practice new levels of caution in terms of social distancing, hygiene, and mask-wearing," Morris said. "Lockdowns achieved this, but at great cost."

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