To reduce something to a lower rank, status, quality, or level of importance.
Combination of 'down' (lower) and 'grade' (level or rank); became common in the 20th century with educational grading systems and then corporate hierarchies.
Credit rating agencies downgrading entire countries' debt in 2008-2012 showed how one word could trigger economic chaos—Moody's and S&P controlled sovereign funding costs with their rating opinions, raising questions about unelected power.
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