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One of humanity’s biggest victories has been the fight against infectious diseases. This battle has led to plummeting rates of child and maternal mortality and dramatically increased life expectancy.

However, there are still large differences in infectious disease rates between different parts of the world. As we might expect, deaths are much less common in high-income countries where almost everyone can access clean water, sanitation, and medication.

One common misconception is that this prosperity has come at the cost of an increase in death rates from chronic diseases, such as heart disease and cancers (collectively called “non-communicable diseases”). But this is not the case. As you can see in the chart, death rates from these diseases are also lower in richer countries. It’s not the case that we’ve simply substituted one health problem for another.

That means that the risk of someone of a given age dying from any cause each year tends to decrease as countries get richer.

Explore more of our data on causes of death across the world →

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Scientists can make an enormous difference in the world.

Take the researcher Sarah Gilbert, who has dedicated her career to developing vaccines. Over the last two decades, she has contributed to vaccines against the flu, MERS, Nipah virus, and Rift Valley fever. When she heard about the outbreak in China in January 2020, she began working on a vaccine, just in case. By the end of that year, the vaccine against COVID-19 was approved, saving an estimated 6.3 million lives in the following year alone. Without this effort, we would have faced a much darker reality, marked by lockdowns, overwhelmed health systems, and widespread suffering.

This chart lists many such scientists whose work saved many people’s lives. The estimates are taken from the web publication Science Heroes, where you can find profiles of these scientists.

It’s difficult to estimate the exact difference particular innovations have made, and I take all such estimates with a grain of salt. None of these scientists did their work in isolation; their innovations were achieved thanks to collaborative efforts and the earlier work of other researchers.

Our team spends much of its time counting deaths, but it’s equally important to know the number of lives saved — even though it is harder to estimate and involves much larger uncertainty. It’s inspiring to be reminded that creative, enterprising, and tenacious people can enormously contribute to our lives.

Fritz Haber and Carl Bosch, who invented synthetic fertilizers, are at the top of this list. My colleague Hannah Ritchie wrote an article about the difference their work has made: How many people does synthetic fertilizer feed? →

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Smokers are about 21 times more likely to die from lung cancer than people who never smoked, and they face increased risks from over a dozen other diseases. I know people who died from smoking: you probably do too.

In 2008, the World Health Organization created a set of tobacco control policies with different tiers, the highest of which are considered “best practices” — they are listed on the chart.

The chart also shows the share of the global population living in countries that had enacted these policies as of 2007 and 2024.

What surprised me is how recent most of these policies still are. In 2007, only a tiny share of the global population benefited from these policies. Since then, coverage has increased across all these measures, but most of them still reach less than half of the world's population.

What is the share of taxes on the retail price of a pack of cigarettes? See the data for each country →