The IMF estimates Eritrea's GDP at $2.1 billion in 2020, or $6.4 billion on a PPP basis. The economy grew at a 3.9% annual rate from 2010 to 2020, an improvement from the 1.3% annual rate from 2000 to 2010. The pickup in growth has been attributed to the commencement of full operations in the gold and silver Bisha mine, the production of cement from the cement factory in Massawa, and investment in Eritrea's copper, zinc, and Colluli potash mining operations by Australian and Chinese mining companies.