Write a question about the following article: From January to June in 2008, 9,078 local tourists and 7,532 foreigners have visited Yala. For the same period of time in 2009 the arrivals have risen to 18,031 locals and foreigners to 10,439. Accordingly, the revenue increased to Rs. 27 millions (235,000) in 2009 from Rs. 16.6 millions (154,000) in 2008. The visitors are allowed to see the wild animals from 5.30 am to 6.30 pm. Due to droughts the park used to be closed to tourists from 1 September, to 15 October annually; however in 2009 and 2010 the closure was skipped and lakes filled with water bowsers for drinking water for the animals, a future strategy on drought handling is not yet clear.

Question about the article:
How many more total tourists visited from January to June of 2009 than January to June 2008?