(Reuters) - The average age of U.S. cars and light trucks rose to a record 12.1 years in 2020, as Americans drove fewer miles and scrapped more vehicles during the COVID-19 pandemic, according to IHS Markit.

The research firm said the two-month increase in vehicles' average age over the 2019 figure could be short-lived as sales of both new and used cars continue to pick up as the pandemic eases.

Vehicle miles traveled in the United States declined more than 13% in 2020, according to IHS, while more than 15 million vehicles were scrapped - about 5.6 percent of the total vehicle population.

Normally, such a high scrappage rate would cause average vehicle age to decline, the firm said. But fewer miles traveled, combined with lower vehicle sales during the pandemic, had the opposite effect, with average age rising from 11.9 years in 2019.

IHS researchers also said an ongoing shortage of semiconductors, which cut into vehicle production, resulted in lower dealer inventories and inflated transaction prices, in turn causing a concurrent rise in used vehicle prices.

The firm said these factors could cause the average vehicle age to go back down in 2021, as more owners sell or trade in their older used vehicles.

(Reporting by Paul Lienert in Detroit; editing by Jonathan Oatis)