The amount of people in the United States who self-identify as "liberal" has climbed to its highest level in two decades, according to a poll released Friday by Gallup.

"Americans' perceptions of their political views — if not the views themselves — are undergoing unmistakable change," Gallup reports, "contributing to greater political polarization in the country."

The shift comes mostly from Democrats, which Gallup suggests are increasingly leaning left. For the first time since Gallup began asking the question in 1992, a "plurality of Democrats consider themselves to be politically liberal, whereas a decade ago, Democrats were most likely to say they were moderate."

While conservatives still make up the majority of U.S. residents, the "conservative advantage" came down 15 percentage points in 2013 when liberals overall rose to 23% of the population and conservatives maintained their numbers at 38%. Those who identify as moderate decreased 9 points since 1992, with 34% now identifying in 2013.

Gallup reports:

When Gallup began asking about ideological identification in all its polls in 1992, an average 17% of Americans said they were liberal. That dipped to 16% in 1995 and 1996, but has gradually increased, exceeding 20% each year since 2005. [...]

The shift toward greater liberal self-identification has been led by Democrats. Currently, 43% of Democrats say they are liberal, a nearly 50% increase from 29% in 2000. Over the same period, the percentage of Democrats identifying as moderate is down to 36% from 44%, and conservative identification is down to 19% from 25%.

Within members of the Republican Party, 70% have consistently described themselves as conservative over the past several years, while 23% identify as moderate and 5% call themselves liberal.

Independents, who hit a record-high of 42% of Americans in 2013, on the other hand, are increasingly calling themselves conservative as members of the Republican party increasingly shift to the Independent label.

However, as Gallup reports, "If the trends in Democratic self-identification continue," the gap between those who identify as conservative and liberal "will likely continue to shrink over time."

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