Rwanda has raised the price of a permit to see mountain gorillas to $750 per day starting June 1, 2012, up from $500. While the price is steep, the program each year raises millions of dollars in revenue for gorilla conservation, including $8 million in Rwanada alone in 2008, according to a 2011 study published in PLoS ONE. The number of permits available each day is limited to reduce the impact of gorilla tourism on the endangered apes. Around 20,000 visited Rwanda\'s gorillas in 2008. The program seems to be working: mountain gorilla populations have steadily increased in recent years, with the combined number in Uganda, Rwanda and Democratic Republic of the Congo reaching 790 in 2010. The opposite trend has been observed with the more numerous lowland gorillas, which are in decline in the Congo basin due to poaching, habitat loss due to deforestation and logging, and disease outbreaks.