By mid-2010, there will be 6.8 billion humans on this planet. According to United Nations estimates, there also will be five billion cellphone subscriptions. These are astonishing numbers. What is still more astonishing, and hopeful, is the breadth of change this number reflects.

The United Nations says that right now 80 percent of the world’s population has available cell coverage. The fastest adoption of cellphone use is occurring in some of the world’s poorest places.

Cellphones are cheap, their batteries can be easily recharged with solar power and they are creating nothing short of a revolution: knitting rural communities together, sowing information, and altering the most basic assumptions about health care and finance. Anyone who has traveled to Africa recently can vouch for these changes.

In nearly every sizable town or city, there are dozens of tiny kiosks where phones can be rented or repaired and subscriptions can be purchased. In regions where communications used to be nearly impossible, cellphones are essential to social innovation. This means everything from microfinance and electronic credit, via SMS, to better networking among health care workers and their patients.

Another revolution is following close on the heels of the cellphone revolution. This year, the number of mobile broadband subscribers — people who access the Internet via laptops or mobile phones — is forecast to pass one billion, up from 600 million at the end of 2009. That number will almost surely skyrocket, too — and the developed world should be doing everything it can to encourage it.

That means increasing the reach and lowering the cost of broadband and pressing for political and commercial openness across the Internet. Mobile communication and access to digital information are powerful development tools and aids to self-sufficiency. And we, in turn, have a lot to learn from the innovative way those tools are being used around the world.