According to Schiffer, Sony's TR-63 radio "cracked open the U.S. market and launched the new industry of consumer microelectronics."[27] By the mid-1950s, American teens had begun buying portable transistor radios in huge numbers, helping to propel the fledgling industry from an estimated 100,000 units in 1955 to 5 million units by the end of 1968.[citation needed]