WASHINGTON/BEIJING - China has seen its national image improve in recent years thanks to strong economic growth, but the country needs more persistent and practical efforts to maintain this progress in the years to come, observers said.

The 2011 Anholt-GfK Roper Nation Brands Index (NBI), released on Wednesday, indicated a slight improvement in China's image, ranking 22nd, compared to 26th in 2008.

The survey has measured the global image of 50 countries annually since 2008, and is conducted among citizens in 20 major countries, including 11 developing countries.

Its results are based on the ratings of responses to questions in six categories - exports, governance, culture, people, tourism and immigration/investment.

China ranked third in cultural heritage this year, the nation's best score, but performed poorly in terms of governance.

Xiaoyan Zhao, senior vice-president at GfK Public Affairs and Corporate Communication, said that fast economic development and the Beijing Olympic Games had helped change public perceptions of China since 2008.

"The Games showed the world the modern side of the country, vibrant cities, stunning architecture and the welcoming people. All of those contributed to the positive image of the country," she said.

The top 10 countries on the Anholt-GfK Roper survey list are all developed nations - the United States, Germany, the United Kingdom, France, Japan, Canada, Italy, Australia, Switzerland and Sweden.

Brazil was the highest ranked developing country at the 20th spot.

The same countries have dominated the top 10 over the years with slight ranking changes because they have consistent reputations and a well-balanced image, Zhao said.

The Chinese government has been paying attention to its national brand building in recent years with investments in hosting international events such as the Olympics and the World Expo, and advertising on the world famous Times Square in New York.

However, Zhang Shengjun, deputy dean of the Institute of Political Science and International Studies at Beijing Normal University, said publicity was only a secondary factor in term of improving China's national image.

"It will surely help, but the root cause is still increased strength. In the current context this means economic growth," he said.

China is now the world's second-largest economy and the largest exporter in terms of volume.

According to the study, China, Japan, Germany, the US and Canada will be the top five influences on global trade and economics over the next 10 years.

But in the export index, China ranked 11th.

Despite a series of economic problems, the US remains the most admired country in the world for the third consecutive year with the best overall reputation, according to the report.

"That's because it's the overall reputation that matters in the case of national image building," Zhang said.

"The strengths of America's international standing continue to be innovation, opportunity and vibrancy," said Simon Anholt, NBI founder and an independent adviser.

"A good image wins fame and attracts substantial interest. But it is not be built overnight, so it cannot be improved overnight," said Fang Lexian, a professor at Renmin University of China, adding that costly one-off campaigns can only help in a very limited way.

"The efforts should be persistent, and it is very important to improve the governance capability to serve the people's interests. The Chinese government did a good job in the evacuation of Chinese nationals from Libya several months ago and won praise for this," he added.

Ouyang Yuanhua contributed to this story.