Which countries emit the most CO2 today? How do annual emissions vary across the world?

There’s not only significant variability in how much CO2 countries emit across the world today. There are also large differences in how much each has emitted in the past. Who has contributed most to global CO2 since 1750?

Our World in Data has been a project many years in the making. Here we detail the history of how the project got started, its evolution over the years and where we are today as a team.

At Our World in Data we present data and research – across more than 3000 charts – on the world’s largest problems. But some metrics are core to our work: here we present 12 that are key to understanding the state of the world.

An estimated 8 million tonnes of plastic enter our oceans each year. But the plastic we find in our surface waters is more than 100-fold lower. This is the ‘missing plastic’ problem.

Maternal mortality was much more common in the past. Today, the number of women that die in childbirth is much lower, but there are still large inequalities across the world. If we can make maternal deaths as rare as they are in the healthiest countries we can save almost 300,000 mothers each year.

The world needs ideas and innovation to make progress against the many problems we face. Creative and talented people that can contribute to this important work are everywhere, but the opportunity to develop is limited to only a small number of well-off children. As a consequence of this, we all – the entire world population – are missing out on the creativity and innovations that would enrich our world and help us move forward.

Social media sites are used by more than two-thirds of all internet users. When did the rise of social media start and what are the largest sites today?

Pregnancy and childbirth are much safer for women today than in the past. But maternal mortality rates are still high in many countries in the world. A woman is 300 to 400 times more likely to die per pregnancy in poor countries than in rich.

For most of our history, pregnancy and childbirth were dangerous for both baby and mother. Whilst maternal mortality has decreased significantly in recent decades, more than 300,000 women die from pregnancy every year.

Growing demand for seafood has placed increasing pressures on wild fish populations. One innovation has helped to alleviate some of the pressure on wild fish catch: aquaculture, the practice of fish and seafood farming. Aquaculture production has now overtaken wild fish catch.

The death of a young child has always been the most devastating tragedy mothers and fathers could experience. How common was it?

Changes in the world population are determined by two metrics: the number of babies born, and number of people dying. How many are born and die every year?

Social media platforms like Facebook reach one-in-three people in the world. In most rich countries the proportion of young people using online social networks exceeds 90%. What does the research tell us about the causal impact of social media use on our well-being?

Our understanding of the world is often shaped by geographical maps. But this tells us nothing about where in the world people live. To understand this, we need to look at population density. How does population density vary across the world?

In the past the average woman had five children. In the past fifty years, this number has halved as a result of women empowerment, declining child mortality and the rising cost of bringing up children.

Every 5th adult in the world smokes tobacco. More than one-third (35%) of men in the world do, but just over 6% of women. How do sex differences in smoking vary across the world?

One-in-five (20%) adults in the world smoke tobacco. But where in the world is smoking most common?

Living conditions are vastly unequal between different places in our world today. Today’s global inequality of opportunity means that what matters most for your living conditions is the good or bad luck of your place of birth. We look at how where you’re born is the strongest determinant of your standard of living, whether in life expectancy, income or education.

Diarrheal diseases remain one of the leading causes of deaths in children. One simple intervention – oral rehydration therapy (ORT) – has saved millions of children in recent decades. Yet it can still do more. We look at the future potential of ORT; barriers to its use; and how many lives it could potentially save.

The world has made significant progress in recent decades in reducing deaths from diarrheal diseases, particularly for children. One of the most successful interventions has been oral rehydration therapy (ORT): a simple salt, water and sugar solution. We look at what ORT is, how it was developed, and how many lives it might have saved.