Premise: It has grown from a few thousand adventurous souls 40 years ago to more than 300,000 visitors a year, and it provides income for Nepalis in mountain villages as well as for those in urban hotels and construction jobs.
Hypothesis: It has grown from a few thousand adventurous souls 40 years ago to more than 300,000 visitors a year due to the immense natural beauty of the area. 
Label: neutral