Complex sentence: With the widespread adoption of cable across the United States in the 1970s and 80s, terrestrial television broadcasts have been in decline; in 2013 it was estimated that about 10% of US households used an antenna.
Split into simpler sentences: With the widespread adoption of cable in the 1970s and 80s, terrestrial television broadcasts have been in decline. In 2013 it was estimated that about 10% of US households used an antenna.