Household income in China surged in the last six years, especially for top earners, putting the country on track to eclipse the United States as the biggest consumer market in a decade, Credit Suisse said in a report on Tuesday.

The bank's survey of 2,700 respondents showed a big rise in property and car purchases, underscoring why many investors are betting big on a rise in China's consumer sector.

The next big theme for China in the new decade is the rise of private consumption, in our view, said Dong Tao, China economist with Credit Suisse in Hong Kong. It is likely to provide a badly needed source of spending for the rest of the world, promoting a global rebalance of trade, consumption and growth.

Based on growth in household income and estimates of economic growth, he expects the share of China's private consumption to GDP to reach 23.1 percent in 2020, just surpassing the U.S. ratio at 22.9 percent. Critics accuse China of contributing to global economic imbalances by saving too much. However, the amount that Chinese consumers save relative to household income has dropped to 12 percent in 2009 from 26 percent in 2004.

Though incomes have been rising across the board, the richest Chinese have been benefiting the most.

The survey data revealed a much bigger income gap than official numbers show, a trend that could have significant long-term social implications. For example, household income rose 50 percent since 2004 for the bottom 20 percent of earners, while the top 10 percent saw a whopping 255 percent rise.

Top earners may invest more in China's booming stock and property markets, accounting for the widening wealth gap.

First-time home buyers are also becoming a big force in China's property market. First-time buyers accounted for 36 percent of the market in 2009 compared with 23 percent in 2006, the survey showed. The share of property bought for investment rose moderately to 18 percent last year from 13 percent in 2006.

The survey was conducted in October and November 2009.

(Reporting by Kevin Plumberg)