The potential for a large, diverse population to coexist peacefully is
thought to depend on the existence of a ``shared reality:'' a public sphere in
which participants are exposed to similar facts about similar topics. A
generation ago, broadcast television news was widely considered to serve this
function; however, since the rise of cable news in the 1990s, critics and
scholars have worried that the corresponding fragmentation and segregation of
audiences along partisan lines has caused this shared reality to be lost. Here
we examine this concern using a unique combination of data sets tracking the
production (since 2012) and consumption (since 2016) of television news content
on the three largest cable and broadcast networks respectively. With regard to
production, we find strong evidence for the ``loss of shared reality
hypothesis:'' while broadcast continues to cover similar topics with similar
language, cable news networks have become increasingly distinct, both from
broadcast news and each other, diverging both in terms of content and language.
With regard to consumption, we find more mixed evidence: while broadcast news
has indeed declined in popularity, it remains the dominant source of news for
roughly 50\% more Americans than does cable; moreover, its decline, while
somewhat attributable to cable, appears driven more by a shift away from news
consumption altogether than a growth in cable consumption. We conclude that
shared reality on US television news is indeed diminishing, but is more robust
than previously thought and is declining for somewhat different reasons