Suppose the value of a network to an individual user is proportional to the number of users. Then the total value of the network, summed across all its users,

Suppose the value of a network to an individual user is proportional to the number of users. Then the total value of the network, summed across all its users, is proportional to the square of the number of users. See also https://en.wikipedia.org/wiki/Network_effect https://en.wikipedia.org/wiki/Network_effect .