OTTAWA—Statistics Canada said Tuesday the economy grew 4.6 percent last year, compared with a decline of 5.2 percent in 2020, the first year of the COVID-19 pandemic. Growth in the fourth quarter came in at an annualized rate of 6.7 percent. Statistics Canada said the largest contributor to economic growth last year was household spending and residential construction as new home construction, resales and renovations increased at near-record levels. The increase of 15.4 percent for the year was second only to the 17.4 percent gain recorded in 1983 as the country came out of a recession the previous year. Household mortgage debt increased by an unprecedented $182.4 billion last year, Statistics Canada said, bringing the total amount of residential mortgages countrywide to $1.93 trillion in December. Output was flat at the end of 2021 as Statistics Canada said real gross domestic product was essentially unchanged in December. That left the …