High-definition television (HDTV) in the United States was introduced in 1998 and has since become increasingly popular and dominant in the television market. Hundreds of HD channels are available in millions of homes and businesses both terrestrially and via subscription services such as satellite, cable and IPTV. HDTV has quickly become the standard, with about 85% of all TVs used being HD as of 2018.[1][failed verification] In the US, the 720p and 1080i formats are used for linear channels, while 1080p is available on a limited basis, mainly for pay-per-view and video on demand content. Some networks have also began transmitting content at 1080p via ATSC 3.0 multiplex channels, with CBS and NBC affiliates being the main stations that transmit at 1080p.