Average fixed mortgage rates in the U.S. edged up in the latest week but still remained below 4%, according to mortgage-finance company Freddie Mac (FMCC).

Freddie Mac Chief Economist Frank Nothaft stated Wednesday that the slightly higher rates followed mixed economic reports. Existing home sales were down 6.1% in November, missing economists' expectations, while third-quarter real gross domestic product was revised sharply higher.

For the week ended Wednesday, the 30-year fixed-rate mortgage averaged 3.83%, compared with 3.8% a week earlier and 4.48% a year earlier. Rates on 15-year fixed-rate mortgages averaged 3.1%, compared with 3.09% the previous week and 3.52% a year earlier.

Five-year Treasury-indexed hybrid adjustable-rate mortgages, or ARMs, on average, were at 3.01%, compared with 2.95% the previous week and 3% a year earlier. One-year Treasury-indexed ARM rates on average were 2.39%, from 2.38% the previous week and 2.56% a year earlier.

Write to Chelsey Dulaney at chelsey.dulaney@wsj.com

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