The SOFIX index, which tracks the 15 most liquid shares on the Bulgarian Stock Exchange, fell by 11.11% in 2011, bourse data showed.
The index ended at 322.11 points in the last trading session of 2011, compared to a close of 362.35 points a year earlier.
Total turnover on the regulated market rose to 174.9 million levs ($116.5 million/89.4 million euro) in 2011 from 145.3 million levs the previous year.
However, the total market capitalisation on the regulated segment fell to 3.12 billion levs in December 2011 from 3.47 billion levs a year earlier.
The broader BG40, which includes the 40 most traded shares, remained almost unchanged in 2011, losing only 0.88% of its value. The BG-REIT, which tracks the performance of real estate investment trusts, was the biggest loser among the bourse indices, declining nearly 12.85% to 264.5 points last year. The BG TotalReturn30, in which companies with a free float of at least 10% have equal weight, gained 18.22% to 51.25 points in 2011.