So, what was the solution that Internet Service Providers (ISPs) came up with? Rather than a flat-rate,
they began switching to usage-based pricing schemes, in which customers are charged based on how
much data they use each month, much like a utility bill. Charging this way sends a different pricing
signal to consumers: instead of a single initial charge each month, they incur a continuous cost for each
additional piece of data they use, as illustrated in Figure 5.6. In this way, each person is deducted for the
congestion she creates in the network by being there in the first place. We will investigate these
differences in detail throughout this section.