Social classes go way back to at least the Middle Ages — but classes such as the “lower class” and the “lower middle class” didn’t become a prominent part of our sociological lexicon ...

Low income then correlates to lower class, and high income to upper class. So this means that if you have a "good" credit ...

“High debt-to-income ratios, where monthly debt payments exceed 40% of your gross monthly income, can indicate lower-class ...