There were an estimated 4.6 billion mobile phone subscriptions at the end of last year, compared with about 1 billion in 2002, the International Telecommunication Union said in a report. In developing nations, 57 percent of people were signed up.
"The rate of progress remains remarkable," the U.N. agency said.
The report tallied cell phone, landline telephone and Internet usage in 159 countries, from the mainly European nations that are most advanced in information technology to those in sub-Saharan Africa that are the least developed.
Internet use has grown, but at a slower pace, the report said.
An estimated 1.7 billion people, or 26 percent of the world's population, were online last year, up from 11 percent in 2002.
Still, four out of five people living in poor countries had no access to the Internet, with China alone comprising a third of the people online in the developing world.
"One important challenge in bringing more people online is the limited availability of fixed broadband access," the report said, noting that such services are mainly in the rich world and China.
It said general access to the Internet, telephones and other technologies was becoming cheaper, with the cost dropping in nearly every country last year. The average cost decline was 15 percent.
In Macao, Hong Kong and Singapore, the prices were lowest compared to people's income. Other countries with relatively low prices include Kuwait, Luxembourg and the United States.
The report also created a table ranking countries according to how frequent and how advanced their people newer technologies.
Sweden topped the list, followed by Luxembourg, South Korea, Denmark, Iceland and Switzerland.
The United States was 19th. China, 79th, and India, 117th, continued to advance but scored low because many millions of their people still were without phone or Internet access.