SAN FRANCISCO - For Kasim Tuman, a Uighur activist living in California, the explanation for the long-simmering resentment between his people and the Han Chinese that boiled over into deadly ethnic riots in northwest China last week is a matter of two numbers: 6 and 40.
The first is the percentage population of Han Chinese in Xinjiang, the Uighurs' native province, prior to the establishment of the People's Republic of China. The second is that percentage today.
"The influx of immigrant Han Chinese is so large that Uighurs have become a minority in their own land," said Tuman, the West Coast coordinator the Uighur American Association.
Beijing's explanation for last week's violence is equally simple: It was the work of overseas Uighurs like Tuman - terrorist organizers, the government says, who manipulated their fellow Muslims back home to embark on a bloody rampage.
As columns of Chinese troops maintain a semblance of calm in Urumqi, the provincial capital where at least 156 died and hundreds more were injured in the deadliest episode of ethnic violence in modern Chinese history, attention both in China and abroad has turned to the question of why.
The riots appeared to have grown out of protests over the killing of Uighurs by a mob of Han Chinese factory workers in Guangdong province angry about the rumored rape of two Han Chinese women in the factory. But as with the Rodney King trial and 1992 Los Angeles race riots, the Guangdong incident was a catalyst for the violence, not an explanation for the violence in and of itself.
Tension between Han Chinese and mostly Muslim Uighurs dates back centuries. In recent years, the struggle has come to be seen by some as an issue of religion. This is thanks in large part to the government's classification of independence-minded Uighurs as terrorists (a shift in rhetoric linked to China's acquiescence in the George W. Bush's War on Terror). But observations by scholars, the reactions of regular Han Chinese and the experiences of Uighurs themselves suggest the conflict is less about Islam and more about economics.
The Urumqi riots produced an explosion of indignation inside China itself. As with riots in Tibet in March of 2008, much of the commentary focused on preferential economic policies directed at the region.
"How many other countries treat minorities as favorably as China does?" one YouTube user wrote in Chinese under a video depicting the riots. "Why are some people still unsatisfied? They don't understand gratitude."
Since the start of its "Go West" campaign in the year 2000, Beijing has invested tens of billions in Xinjiang in an effort to develop its rich stores of oil (China's second-largest), uranium, gold and other minerals. Such investment is described in Chinese state media as a boon to Uighurs and other minorities in Xinjiang - a sort of ethnic minority stimulus plan. While the region's GDP growth has hovered in the teens, however, the practical benefits to Xinjiang natives have been meager.
"In key business sectors such as energy, industry, as well as most white-collar sectors, ethnic minorities, particularly the largest group, the Uighurs, have been systematically excluded from employment," Arienne Dwyer, a Xinjiang expert at the University of Kansas, wrote in an email. "This is an inter-ethnic conflict over autonomy and access to resources."
The government doesn't break down income figures by ethnicity, but Tuman suggests those who doubt the disparity can make quick visit to his hometown.
"Just go to Kashar and look around," he said. "During the day, the streets are filled with Uighurs. But you go out at night and it's all Han. Why? Because the Han Chinese have the jobs. They're working during the day."
It's a pattern that reaches back through the centuries. Writing about the most successful Uighur revolt against Chinese rule - the Muslim Rebellion of 1864, when Uighurs and ethnic Chinese Muslims chased out Qing Dynasty troops and succeeded in establishing the state of East Turkestan (1864-1877) - historian James Millward argues it wasn't religious conflict but instead "economic distress and rampant misrule from the 1850s that created the conditions underlying the uprisings."
In the Xinjiang of the current era, economics and culture have become entangled in complex, and potentially explosive, ways. An example is the government's decision in 2002 to replace the "out of touch" Uighur language with Mandarin in the region's classrooms. Sold by officials as an effort to help Uighurs integrate more smoothly into the modern economy, it was seen by many Uighurs as an attack on their very existence as a people.
In the eyes of many regular Chinese people, the policy seems reasonable enough.
"I think a lot of Han Chinese are being genuine when they say they don't understand why Uighurs don't appreciate what the government is doing for them," said one American scholar who preferred to remain anonymous to preserve research access to Xinjiang.
"It's matter of different ideas about what development means," the scholar added. "The way Americans are about democracy, it's the same way Han Chinese feel about their economic model."
While he believes the only true solution to the Han-Uighur conflict is the establishment of a new East Turkestan, Tuman is realistic enough to acknowledge China has far too much invested in Xinjiang to let that happen in the foreseeable future. He suggests that as an interim solution Beijing set up an independent unit of the provincial government to represent the concerns of Uighurs with real power to change policy.
"I can understand the idea of government as parents looking out their children's interests," he says. "The problem is this government isn't doing a good job of parenting."
But with last week's violence having stoked the ethnic animosity in China to toxic levels, Tuman isn't hopeful even that step will be taken. "This is a terrible disaster for us," he says. "It's only going to lead to more killing, which will generate even more hatred."