Fitch Ratings has upgraded Russian diamond producer ALROSA’s Long-Term Issuer Default Rating (IDR) to ‘BB+’ from ‘BB’, the agency said in a press release on Wednesday. The company’s Short-Term IDR has been affirmed at ‘B’. The outlook on the Long-Term IDR is stable, the report said.

“This is a result of Alrosa’s outperformance of our conservative expectations over the past few years, driven by a weaker rouble and higher than expected diamond pricing,” Fitch said. The ratings also reflect the company’s strong operating profile as the largest diamond producer (30% global diamond production share in 2015), and its cost leadership, the report said.

Alrosa, which operates in Russia’s Republic of Sakha (Yakutia), is among the top ten of Russia’s most efficient enterprises. The company accounts for 94% of Russia’s overall diamond output, and for 25% in the global diamond production in terms of value. Alrosa’s probable reserves make up about one third of the world’s diamond resources. The company has its own advanced exploration complex enabling it to maintain and expand its proven reserves. Its diamond production equaled 38.3 mln carats and sales amounted to 30 mln carats in 2015.