The Economist's Democracy Index finds that the gradual erosion of democracy around the world continued last year, with 89 of 167 countries in the rankings considered less democratic thank the year prior.

The world's 10 strongest democracies: Norway, Iceland, Sweden, New Zealand, Denmark, Ireland, Canada, Australia, Finland, Switzerland. The U.S. is 21st, and considered a "flawed democracy."

Norway, Iceland, Sweden, New Zealand, Denmark, Ireland, Canada, Australia, Finland, Switzerland. The U.S. is 21st, and considered a "flawed democracy." Big movers: Venezuela is now considered authoritarian, with Indonesia also dropping significantly. The Gambia took the biggest step forward.

Venezuela is now considered authoritarian, with Indonesia also dropping significantly. The Gambia took the biggest step forward. Why it matters: In the second half of the 20th century, there was a strong trend toward more democracy around the world. That trend is now in reverse.

Go deeper with a great video from the NY Times' The Interpreter on this topic