The death of a child has always been the most tragic calamity mothers and fathers could experience. How common was it that parents saw their children die?

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.

Diarrheal diseases are one the largest killers of children, responsible for more than half a million child deaths in 2017. Rotavirus is the leading cause of diarrheal deaths in children. There is, however, an effective tool against it: the rotavirus vaccine. We look at rotavirus vaccine coverage across the world; the estimated number of lives saved and its potential to save more children.

Despite being treatable and preventable, 1.6 million people died from diarrheal diseases in 2017; one-third were children under five years old. This makes it one of the largest killers of children. Here we look at where and why children are dying from diarrrheal diseases, and what we can do stop this.

15,000 children under five years old die every day. To reduce this figure we need to understand what children are dying from, and what interventions are available to stop this. Here we look at the number of children dying by each cause – from pneumonia to diarrheal diseases, malaria and malnutrition. We also present the range of interventions that are available to prevent children from dying.

15,000 children under five years old die every day. If we want to save as many children as possible, we need to first understand where children are dying. Here we look at how countries compare in the number of child deaths, and how this has changed over the past few decades.

Child mortality – one of the most important aspects of development – has always been a focus for us. But in our new Our World in Data series we want to go further than this: exploring in detail the differences in child mortality across the world; what children are dying from; and what we can really do about it.

How does sex ratio at birth vary across the world? We might expect that naturally an equal number of boys and girls are born, but this is not the case. There are biological reasons why more boys than girls are born each year: around 105 boys per 100 girls. But in countries with a strong son preference, the sex ratio is even more skewed.

Vaccines have provided some of the greatest interventions to global health to date. But attitudes to vaccination – whether they are safe, effective and important – are often divisive. Here we look at results from the largest global survey to date – the Wellcome Global Monitor – on attitudes to vaccination across the world. 92% of the world thinks vaccines are important for children to have, but in some countries skepticism on their safety is as high as 1-in-3.

92% of people in the world think vaccines are important for children to have. But in some countries, skepticism about their safety is as high – in some cases every 3rd person. What effect do public attitudes have on vaccine coverage rates, and what can we do about skepticism to vaccines?

Are we happier when we spend more time with others? Studies suggest social relations are key factor in happiness & life satisfaction. We take a closer look at the evidence for how much social connections matter for happiness.

Loneliness has been reported to be as lethal as ’15 cigarettes a day’. What is the evidence for this? We take a deeper look at the data and research on the link between loneliness and health and wellbeing.