Bulgaria's population has declined by 11.5 per cent in the past decade, according to first results from the 2021 census.
The National Statistical Institute said that the nation has shrunk by 844,000 people, from some 7.3 million in 2011 to 6.5 million today.
Experts attribute the decline to low birth rates, high mortality, and a steady migration flow that has seen working-age people leaving to look for better jobs and education prospects in Western Europe and beyond.
"This is the most drastic decrease registered so far," Magdalena Kostova from the statistical institute told reporters. "The aging of the population is another lasting trend."
Bulgaria has for years been on the radar of the UN as one of the nations with the fastest shrinking population in the world.
Since the Balkan nation moved from a totalitarian system to a free-market economy three decades ago, its population has decreased by nearly a quarter, from almost 9 million to 6.5 million today.
UN experts estimate that if these trends continue, Bulgaria will contract further to about 5.4 million people by 2050.