Today, rock music is centered on almost exclusively in Beijing and Shanghai, and has very limited influence over Chinese society. Wuhan and Sichuan are sometimes considered pockets of rock music culture as well. It points to a significant cultural, political and social difference that exist between China, the West, or even different parts within China. While rock has existed in China for decades, the milestone that put the genre on the international map is when Cui Jian played with The Rolling Stones in 2003, at the age of 42. China has also become a destination of major Western rock and pop artists; many foreign acts have toured in China and performed in multiple concerts in recent decades, including Beyonce, Eric Clapton, Nine Inch Nails, Avril Lavigne, Linkin Park and Talib Kweli. Mainland China has a high piracy rate along with issues of intellectual properties. Normally there is some delay before the products are released into mainland China, with occasional exceptions, such as the work of Cui Jian who was released in Taiwan, Hong Kong and mainland China simultaneously. Consequently, a delay in release time is also the biggest driver of piracy, since individuals would rather pirate from the outside. The modern market is not only hindered by rights issues, as there are many other factors such as profit margin, income and other economical questions. In 2015, the digital music market in China was expected to be worth . In 2015 China had the 14th largest music market in the world, with revenues of . As of 2016 there were 213 music charts in China. Also as of 2016, the three largest music streaming and download services in China are KuGou, with a 28% share of the market, QQ Music with 15% and Kuwo with 13%. China is expected to become one of the largest music markets in the world by 2020. Traditional music Instrumental Musical instruments were traditionally classified into eight categories known as bayin. Traditional music in China is played on solo instruments or in small ensembles of plucked and bowed stringed instruments, flutes, and various cymbals, gongs, and drums. The scale is pentatonic. Bamboo pipes and qin are among the oldest known musical instruments from China; instruments are traditionally divided into categories based on their material of composition: animal skins, gourd, bamboo, wood, silk, earth/clay, metal, and stone. Chinese orchestras traditionally consist of bowed strings, woodwinds, plucked strings