Elevated programming tiers commonly start with an expanded basic package, offering a selection of subscription channels intended for wide distribution (primarily those that launched between the 1970s and the 1990s); since the upspring of digital cable and satellite television during the mid- and late 1990s, additional channels with more limited distribution are offered as add-ons to the basic packages through separate tiers, which are commonly organized based on the programming format of the channels sold in the tier.