Map of the day: What’s holding Apple back in the developing world

Source: Click to enlarge.

FORTUNE — Apple (AAPL) made headlines last month on reports that its iPhone shipments to India tripled in the space of six months. Since then it’s instituted some aggressive marketing techniques, including an advertising blitz and a buyback scheme, that could propel the company’s sales in the country, according to one estimate, to $1 billion before the end of fiscal 2013.

But the real limiting factor for Apple in India — and other emerging markets — may not the phone’s price as much as the issue apparent in the OpenSignal map above: The vast portions of the subcontinent with no 3G and 4G cellular coverage.

Asymco‘s Horace Dediu stated the problem succinctly earlier this week in this exchange with The Next Web‘s Martin Bryant:

TNW: At what point do you believe that the majority of people in emerging markets will own smartphones (if at all)? 

Dediu: The question is academic. The more important question is when will mobile broadband be available to all those who own smartphones. The economics of providing bandwidth are out of sync with the economics of providing terminals that can consume it. If it continues this way, all those smartphones will not be used for mobile data and will thus be essentially dumb.

Full transcript: Horace Dediu on the bad habits of Apple analysts and why Tim Cook shouldn’t be fired.

Subscribe to Well Adjusted, our newsletter full of simple strategies to work smarter and live better, from the Fortune Well team. Sign up today.