Alongside merchants and armies, history's great powers have exported curious citizens to consume far-off wonders and serve as walking advertisements of their kingdom's wealth and reach.

Roman patricians built holiday homes all around the ancient world, from Sicily to Greece to Carthage; young Renaissance elites embarked upon customary "grand tours" of Europe; Britain's Victorian middle classes, flush with new leisure time and money, fanned out to so many exotic locales that the 19th century British Member of Parliament and journalist Henry Labouchere allegedly joked, "Go where you may, to the top of a pyramid or to the top of Mont Blanc, you are sure to meet an Englishman."

More recently, America's postwar golden hordes and the snapshot happy Japanese have become potent symbols of the high living standards and disposable incomes of their home countries.

Now it's the Chinese century, and as we emerge from the recession, Chinese tourists are poised to lead the world into a new era of adventure and spending, where boundaries-- physical, psychological, and otherwise-- exist only to be shattered. Twenty years ago, Mainland Chinese rarely headed abroad for sightseeing or shopping. Not only were the vast majority too poor to afford such travel, the government tightly controlled their movements.

But thanks to a series of changes-- including the establishment of three official Golden Week holidays in 1999; the easing of travel restrictions, first to neighbouring Asian countries, then to the Middle-East and Europe from 2002 to 2004, and finally to the US in 2007; and the country's growing affluence and expanding middle class - Chinese tourism has ballooned over the past decade.

According to the state-run China Tourism Academy, 54 million Chinese are expected to go abroad this year, up from 47,6 million in 2009 and a mere 10,5 million in 2000.

And thanks to Asia's resilience during the financial crisis, while global international travel fell 4 percent last year, intra-Asian tourism was up 2 percent, led by visitors from China.

Analysts predict these numbers will keep expanding. Right now, China's outbound tourism represents a mere 4 percent of its population.

That makes China today comparable to Japan in the 1980s or South Korea in the 1990s, according to Hong Kong based analyst CLSA. But both those countries now average outbound departure rates of about 15 percent.

The World Tourism Organisation, which says visits by the Chinese have grown at an annual average rate of 22 percent since 2000-- estimates that by 2020, mainland travellers will take 100 million trips abroad, making China the world's fourth-largest source of overseas tourism.

So who are these travellers? First off, most Chinese tourists-- some 75 percent-- still restrict their trips to Hong Kong and Macau. Of the remainder, more than half stay in Asia, with only 10 percent venturing to Europe or the US still, their impact on the countries they visit is significant: China is now the second largest source of tourists to Singapore (after Indonesia), Nepal (after India) and Taiwan (after Japan, though the two countries are expected to switch places this year).

It's the largest supplier of tourists to Vietnam, Macau, and Hong Kong. Indeed, last year Hong Kong recorded 18 million Mainland Chinese visitor arrivals-- more than twice as many people as live in the city. Japan, South Korea, and Thailand are among the other top destinations, but experts predict that China will soon look farther afield: Europe and particularly France-- ranks high on China's wish list, and the number of Chinese travelling to Britain jumped 33 percent in the past five years.

Likewise, the US travel Association says that china was one of the few countries to increase visits to America in 2009, and it expects the number of Chinese tourist arrivals to grow from a half million last year to 795 000 in 2013.

National tourism industries are racing to woo these new visitors-- especially because the activities highest on their to-do lists are shopping and gambling.

Chinese tourists dropped an average of US$1 000 per person on retail goods while in Britain last year-- up 83 percent over 2008, according to the shopping service Global Blue and they outspent both Russian and Japanese tourists in France. They are the highest-spending international visitors in the US, pumping an average of US$7 200 per person, per trip, into the economy.

In Hong Kong, Chinese tourists spend 80 percent more than the Japanese on shopping, according to a CLSA study. They are mainly in the market for cosmetics and luxury labels-- Rolex, Burberry, Gucci, Louis Vuitton, Chanel-- because these goods are far cheaper abroad than in China, where duty taxes are high, and because shoppers needn't worry about the risk of fakes, as they do at home.

Retailers have picked up on their love of spending: august Parisian institutions like Printemps are hiring Chinese speaking staff, while the head of Galeries Lafayette was quoted as saying the Chinese have surpassed the Japanese as the store's "No. 1 foreign customers."

High-end brands such as Cartier have taken to hosting private parties for Chinese tour groups, and other companies offer to help Chinese travel agents book restaurants and hotels in exchange for bringing guests by their stores.

In Southeast Asia, many mainland agents make their money by sending groups to local retailers in exchange for a cut of the sales. In Malaysia, Vietnam, and Macau where half of all mainland travellers cite "entertainment" as their primary purpose for going-- casino construction is flourishing. Singapore, a top Chinese destination, also recently overturned a 40-year ban on casino building.

While the Chinese like to gamble, they don't seem to care much where they stay; one study notes that the percentage of money Chinese tourists allocate to lodging has fallen from 16 to 10 percent in the past five years (not coincidentally, shopping expenditures rose the same amount in that time period). Yet despite their avid consumption of luxury goods, Chinese travellers have drawn criticism for their less than classy behaviour.

The majority of complaints come from neighbouring Asian countries-- not surprising, since the guest host interactions there are more loaded than in Europe with the weight of shared, and often bloody, history.

Some tour guides in Vietnam, where memories of the 1979 border war still linger, report that the Chinese "look down on them."

By contrast, in Hong Kong and Singapore the mainlanders are often stereotyped as country bumpkins unaccustomed to the slick urban ways of their expert cousins. The Hong Kong media regularly lambast mainland tourists, showing pictures of them squatting and letting children urinate in public, for example, or going barefoot on the grounds of Hong Kong Disneyland on its opening day in 2005. A Straits Times article the same year titled "The Rise of the Ugly China tourist" further fanned the flames by painting mainland travellers as hopelessly loud, rude, and uncouth.

Beijing has not taken the accusations of bad behaviour lightly. Shortly after the Disneyland incident, the official Xinhua News Agency warned that spitting, slurping food, and jumping in line are "intolerable" in other countries. And in 2006 the National Tourism Administration and the Civilisation Office published a guide to travel dos (be polite, respect lines, observe "ladies first") and don'ts (litter, take off socks in public, haggle in department stores). These official responses to Chinese behaviour abroad demonstrate Beijing's fear that bad etiquette tarnishes the modern superpower image the government is working so hard to project. It also indicates a deeper ambivalence in the party over allowing tourists to roam freely in foreign lands. On the one hand, Chinese travellers are showcasing the country's awesome new spending power.

But there's also the worry that Chinese could come into contact with dangerous foreign cultures-and ideas. Scholars such as Pal Nyiri have noted that some official tourist manuals include sections on avoiding the disclosure of state secrets, and warn Chinese to be cautious in dealing with foreigners, especially in discussing political views.

As more and more main-landers turn to tourism as a leisure activity, it will be increasingly difficult to control the contact between Chinese and locals.

Certainly, Chinese tourists are going to change the world over the next decade. But the world might just end up changing them in return.