The difficulty is what adjusts the distributed time function of the network to stay on target, so that the inflation is controlled, measured in Bitcoins. The Bi

The difficulty is what adjusts the distributed time function of the network to stay on target, so that the inflation is controlled, measured in Bitcoins. The Bitcoin network only knows about Bitcoins, not how much USD it trades for. When the blocks being mined approximately every 10 minutes is valued higher in USD, naturally more people want more of those blocks. So the miners expand simply to compete, since what they compete for is worth more.