In the year 2020, a smartphone is seen more as a necessity than a luxury -- going without one means missing out on the many advantages to be had with internet connectivity in your pocket. But for billions of people around the world, owning a smartphone is still prohibitively expensive.

According to a survey published Thursday by the Alliance for Affordable Internet, an initiative of Tim Berners-Lee's Web Foundation, 2.5 billion people live in countries where a smartphone costs a quarter or more of their monthly income. In some countries, the cost of a device is higher still, locking people out of phone ownership, and internet access with it.

In Sierra Leone, for example, the average person must pay more than six months of income to afford a smartphone, which would set them back $256. In India, where a fifth of the global population lives, the cheapest smartphone offered by leading carrier Jio costs $346 -- more than twice the average monthly salary. The cost of a smartphone in Burundi is lower, at $56, but for most people this is equal to 221% of their average monthly income.

The survey was conducted across 70 low- and middle-income countries, and found huge disparities between how affordable smartphones were in the different nations.

The survey also found that women are more likely to be priced out of smartphone ownership than men, who are 25% more likely to own a smartphone. Women's more limited spending power also means that when they do own a phone, it's likely to be older and have less functionality than those owned by men.

Getting more people online is one of the big goals of the Web Foundation, as well as the United Nations and many national governments. Internet access can improve education and employment opportunities, as well as access to key services, ultimately boosting economic growth. Back in April, Web Foundation research showed that we're likely to miss a big UN internet access goal this year -- meanwhile, the coronavirus pandemic raging around the globe has shown just how essential the internet is to keeping society functioning.

"COVID-19 has shown that to be without internet access can mean missing out on critical health advice, losing your livelihood and being cut off from your loved ones when physical distancing becomes the norm," the Web Foundation's research director, Teddy Woodhouse, said in a statement. "The internet is a lifeline, and we need to do everything possible to remove the barriers that stand in the way of people getting online."

Boosting the number of people able to get online globally is reliant on several factors, including making the internet accessible and affordable to people regardless of their location or socioeconomic status. But affordable data packages are meaningless if people can't also afford to buy the devices they need to access the internet in the first place.

Phones are "essential doorways" to the internet, said Woodhouse. "The vast majority of the next billion people who come online will do so using a mobile device, and so if we're to make sure more people can access the internet's benefits, handsets must be more affordable."

In its report, the Alliance for Affordable Internet acknowledges that a number of factors determine the basic cost of manufacturing and marketing a smartphone. But it also says there are a number of steps governments and multilateral bodies can take to help, including reducing taxes on low-cost devices and supporting projects that help people spread the cost of devices.