That 90% figure is suspect as well, since it's including the initial buildout costs of young projects in the financial calculation. So the authors don't consid

That 90% figure is suspect as well, since it's including the initial buildout costs of young projects in the financial calculation. So the authors don't consider it "sustainable" until the buildout costs are fully paid off. It's considered a failure if they took out a loan to build out the network.