Every year at the Asia-Pacific Economic Cooperation (APEC) Economic Leaders' Meeting, leaders from 21 Pacific Rim member states meet to discuss the big issues. This year, for instance, huge trade deals and geopolitical rivalries are among the major topics of conversation.

These are some of the most important leaders in the world, together representing more than half of the world's GDP and encompassing heavyweights such as the United States, China and Russia. But each year, it's often the guests' attire that captivates the world more than any political talk.

That's because APEC has an unusual tradition. At the summit, the leaders gather to take a "family photo," and for more than a decade these leaders have often been photographed wearing clothing that represents the country hosting the event. For example, this year the event is being held in Beijing, and the leaders wore some bright colored silk outfits, which look like they might be modeled on the famous Zhongshan suit.

The event sometimes earns the nickname of the "silly shirts" photo, and various world leaders (including Americans) have tried to do away with it. But American readers might need to be reminded that they started this tradition with their own traditional clothing: And it actually wasn't a shirt.

The tradition began in 1993 on Washington state's Blake Island, site of the first APEC meeting to be attended by heads of state rather than ministerial-level officials. The world leaders were asked to not wear ties; an attempt to cut down down on the formality that high-level meetings usually involve. APEC, which is about working together to improve relationships, had no time for formality.

Clinton gave the world leaders leather bombardier jackets as a gift, like those worn by American pilots. Judging from photos, the world leaders may not have actually worn their jackets publicly at the time -- most featured only Clinton clad in leather, and many news stories from the time made no mention of it.

Even so, it became a trend. The next year, the event was held in Indonesia, and those in attendance wore loud batik shirts at the request of their hosts. Over the years, it has become a fun tradition: World leaders wore barongs in the Philippines, hanboks in South Korea, raincoats in Australia, ponchos in Chile and leather jackets (again) in Canada, among many others.

At some point, the sartorial aspect of the APEC summit became a key element of the event. In 2010, Reuters' Bill Tarrant -- a reporter who had covered the 1995 batik shirt summit in Indonesia -- explained why clothing was so important at APEC:

The APEC Leaders’ parade does serve a useful purpose. First of all, it delights the photographers and TV camermen who have been working day and night for a week  to take excruciatingly boring images of talking heads. The show gives everybody a chuckle as they ponder the fact that once again the Leaders’ Declaration has said essentially very little of substance. The group operates by consensus and has no framework to negotiate binding agreements. Its biggest achievement may well be its annual show of harmony and singing kumbaya in a region of great power rivalries and geopolitical tensions.

That doesn't mean that the tradition is always upheld. For a while, it looked like the trend might die out.

In 1995, for instance, the Japanese decided that wearing traditional outfits would be problematic: Kimonos were apparently thought to be too bright and too figure-hugging for the more demure world leaders, and business casual better fit the mood of Japan at the time. A similar decision was made in 2010, when Japan hosted the summit again.

And while Barack Obama initially joked that world leaders would soon be "all decked out in flowered shirts and grass skirts," when they actually visited Hawaii in 2011, the U.S. president later changed his mind: While the attendees were given aloha shirts, they were not required to wear them.

"I got rid of the Hawaiian shirts because I looked at pictures of some of the previous APEC meetings and some of the garb that appeared previously and I thought this might be a tradition that we might want to break," Obama said during the summit. "I suggested to leaders, we gave them a shirt and I promise you if they wanted to wear it that would have been fine, but I didn't hear a lot of complaints about breaking precedent."

Apparently not all world leaders were impressed. "Where are the Hawaiian shirts?" Chilean President Sebastian Pinera Echenique asked Obama. "We are ending that tradition," Obama explained. In 2012, the Russian hosts again went without the "silly shirts."

This is apparently a trend that won't die, however. Following calls for a return to the "silly shirts" in the press and online, Indonesia brought back the tradition in 2013, asking world leaders to wear shirts made from the silk-like Balinese fabric called "endek." The shirts even carried a dual meaning: While the fabric came from Indonesia, it was woven in China. Fitting symbolism for a summit about free trade.