Few human experiences are as universal – or as poorly understood – as loneliness.

More than just a blue feeling and the inspiration for countless songs, it’s linked to poorer wellbeing, worse mental and physical health and a higher risk of early death.

Even in the age of social media, we hear of loneliness being on the rise everywhere – to the extent that some have labelled it an epidemic.

To build a better picture, we analysed responses to the Gallup World Poll from more than 218,000 people, across nearly 150 countries. We found around one in five people reported feeling lonely during a typical day.

But that global average masked a stark divide.

In high-income countries, 15.7% of people reported loneliness, including 16.2% in New Zealand and 17.8% in Australia. In low-income countries, by contrast, nearly one in three people (31.3%) reported feeling lonely.

The findings challenge the classic idea that loneliness is simply a private struggle. Instead, they suggest it is also a social........

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