20853
Skateboarding has been slow to develop in China because of the lack of a strong preexisting street culture and of skating infrastructure ; nevertheless , it 's estimated that as of 2009 there are 40,000 to 50,000 skateboarders in China .
 Skateboarding
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Skateboarding