Gambling enterprises on tribal lands employed about 327,000 people, led to about $80.7 billion in output to the U.S. economy and generated $11.7 billion in taxes, according to the Indian Gaming Industry Report by Alan Meister, an economist with the Analysis Group consulting firm in Los Angeles.

Indian gambling is intended by law to build and sustain self-sufficient tribal governments, and experts say it generally has met its goal, though some tribes have benefited more than others.

A total of 228 tribes use gambling revenues to fund tribal governments and support social services such as health care, housing and education.

About 34 per cent of tribes distribute direct payments to tribal members, the report showed.

Last year's revenue growth rate is the lowest since 1988, when the Indian Gaming Regulatory Act was passed, the report showed.

The total number of Indian gambling facilities – 423 – increased by just one in 2006, compared with an increase of 10 in 2005. There's also more competition from non-Indian gambling and racetracks with slot machines.