1. 1. 11 Walkman, the analogue predecessor to the iPod, was invented by the consumer electronics company Sony and first produced in 1979. This metal-cased blue-and-silver portable cassette player allowed peo ple to listen to music while on the move. Initially priced at $150, it was bought by more than 50,000 people in the first two months of its release. Soon it became a must-have gadget for every teen. However, as of October 2010, after selling about 200 million cassette based Walkmans, Sony discontinued their production. Use graphs to explain why a monopoly exits a market when its demand curve shifts to the left.