Multifamily fundamentals weakened in Q4 2020 as COVID-19 continues to take a toll on the U.S. economy. The vacancy rate for our national sample of properties increased 40 basis points (bps) year-over-year to 4.5%. Average monthly rents posted their largest Y-o-Y decline in 10 years, falling 4.2% to $1,666.49. The supply pipeline remains strong, with stock growing a healthy 1.7% Y-o-Y.
Economic indicators are still in negative territory but continue to improve. According to an advance estimate of Bureau of Economic Analysis, the U.S. economy grew at 4.0% (annualized rate) in Q4. The December 2020 unemployment rate stabilized at 6.7%, a considerable decline from 14.7% recorded in April, but still above 3.5% recorded in March 2020. With increased immunization and new economic stimulus on the horizon, we expect the U.S. economic recovery to accelerate throughout 2021, with new household formation rising, and the reopening of major metros spurring recovery in the apartment sector.
Due to outmigration, rents fell furthest in major metropolitan markets. With remote working allowing employees to live further from the office, and many of the amenities in major metros still shuttered, rental demand has shifted toward secondary and tertiary metros where renters can find more space at a lower cost. We expect this trend to be temporary, with demand shifting back to major metros from H2 2021 through 2022, as workers return to the office and renters compete to lock in lower rents before they rise to pre-COVID levels.
We expect national multifamily fundamentals to bottom out in early 2021 and to recover by mid-2022, with secondary markets leading the recovery in early 2022, followed by major metros. Vacancy is expected to rise to 5.2% at its highest point, while rents are expected to fall 5.7% from pre-COVID levels at their lowest point, both occurring in Q2 2021. The long-term outlook for multifamily remains strong, with both rent and vacancy expected to recover to pre-COVID levels by Q2 2022.