Although the invention of cordless telephony dates back to the end of the 19th century, the first mobile phones for the public did not appear until the 1950s in the United States and were initially sold as automotive equipment. It was not until the 1970s that the first truly portable (but far from pocket-sized) devices appeared. Even during the development of the GSM system in the 1980s, it was assumed that only a small part of the population would use mobile phones in developed countries. Thanks to lower deployment costs and faster deployment of any necessary terrestrial technologies, mobile networks have been able to spread faster around the world, outpacing the growth and, consequently, the expansion of fixed telephony. At present, the number of telephone subscribers is comparable to the population of the Earth.