To highlight the sheer uselessness if not outright stupidity of G-20 meetings, one need only look at the alleged main achievement of the boondoggle:

"The G-20 endorsed setting up a global body monitoring steel overproduction."

The Wall Street Journal reports G-20 Reaches 'Broad Consensus' on Supporting Global Economy, China's Xi Jinping Says.

China rallied the Group of 20 around a call to use new levers to revive global growth, though the group's nine-page statement was short on concrete steps and there were few signs that Beijing would lead by example.

Speaking at the conclusion of the meeting, the International Monetary Fund's Christine Lagarde said, "There must be more growth and growth must be more inclusive."

In opening the summit, Mr. Xi urged leaders from major economies to be an "action team" rather than a "talk shop." Ahead of a spectacular gala performance Sunday night, he pointed to the logo the host country designed for the summit — a stylized bridge consisting of 20 lines in light green — as Beijing's way of promoting international cooperation.

"The Group of 20 is like a bridge, bringing together people from all over the world," Mr. Xi said.

For foreign delegates, the event reinforced a sense of China's power, including its capacity to nearly empty a city of nine million. Offers of vacations and encouragement for residents to go out of town had turned Hangzhou into a ghost town of empty streets for the meeting.

Behind closed doors and in press conference, China faced pressure from its guests. According to one European official, tensions over the communiqué adopted by G-20 leaders revolved around steel from China, which produces half the world's supply.

"If you're looking for blood, steel overcapacity was the issue," the official said.

In the end, the G-20 endorsed setting up a global body monitoring steel overproduction—a result the official said was Europe's main achievement at the summit.

The final communiqué, as others at G-20 gatherings before it, didn't single out China, saying, "We recognize that excess capacity in steel and other industries is a global issue which requires collective responses."

Ding Xuedong, chairman of China Investment Corp., the country's giant sovereign-wealth fund, said he has noticed a rising tide against globalization.

"We'll need to improve communication with other countries and enhance transparency," he said.