The rating upgrade by Moody’s comes almost exactly 10 years after it downgraded the city’s rating, citing low oil prices and high debt at the time. Dominic Anthony Walsh / Houston Public MediaThis week, the city of Houston's credit rating was upgraded for the first time in years. Moody's Ratings, one of several global financial rating services, increased Houston's bond rating from Aa3 to Aa2 — the third-highest rating available. The rating upgrade comes almost exactly 10 years after Moody’s downgraded the city's rating, citing low oil prices and high debt at the time. "So the bondholders are loaning money to the city, and they just want to see a stable financial system," he said.