Internet speed, fixed and mobile networks in developing nations

Earlier this week while introducing some bright, undergraduate students to the NetIndex explorer on Ookla's website (the subject of this earlier post) I had occasion to ask them the following question.  Why does the big difference between Korea or Japan and many African nations (e.g. Korea 54 Mbps, Tanzania 4.2 Mbps) in average internet download speed matter?  Put otherwise, why is the difference important?  The discussion that followed, along with several alerts that arrived in my e-mail this morning, prompted this post.
The McKinsey Group, using World Bank Data, recently published a blog post and a longer white paper entitled Offline and falling behind:  Barriers to Internet adoption.  The study suggests that there are four categories of consumer-facing barriers to Internet adoption, grouped as 1) incentives, 2)low incomes and affordability, 3)user capacity and 4)infrastructure.  On the important topic of network infrastructure, this is one of the first studies I've seen that explicitly acknowledges the important relationship between fixed and mobile networks.  As shown in an exhibit from the study (click to see a full-sized version of the graphic above) fixed broadband penetration is significantly higher in developed nations than in the developing ones.  Measured by household penetration, South Korea leads the world, and by a considerable margin over my home country, the U.S.A.

Another graph (click for larger version) from the study shows clearly that a majority of people in the world still do not have access to 3G or faster mobile networks that allow efficient access and use of many bandwidth-intensive internet services.  A full 70 percent of the mobile connections in the world's two most populous nations, China and India, are on 2G networks.  Of course, this situation will change as developing nations build faster mobile broadband infrastructures.  However, the problem is actually more complex than that.  Fast mobile broadband networks cannot be built with mobile technologies alone for technical and physical reasons.  The electromagnetic spectrum is a finite physical resource, which contains only a small fraction of the bandwidth provided by fiber optic cable.  Fixed fiber optic networks interconnect with mobile ones and complement them by providing back-haul service.  Indeed, Korea's experience would suggest that developing nations have little choice but to address the longer-term, more expensive project of extending fiber optic networks to the people, alongside their efforts to extend mobile networks.