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American swimmers are the main reason why Team USA leads all countries in the Olympic medal count.
Team USA enters the final three days of Olympic competition with a commanding lead in the medal count, well ahead of arch-rival China. The advance follows historic performances Thursday by the U.S. women’s soccer squad, 17-year-old boxer Claressa Shields and decathletes Ashton Eaton and Trey Hardee.
America has 90 total medals, 39 of them gold. China has 80 total, 37 gold. Russia is third with 56 total medals, including 12 gold, and host Great Britain is in fourth with 52 total medals, 25 gold.
Team USA hopes to add to its cache of precious metal Friday at Olympic Stadium, where the women’s 4x100m relay team hopes to win America’s first title in the event since 1996. The race starts at 3:40 p.m. ET.
Brad Walker will compete in the men's pole vault final at 2 p.m. ET, and Molly Huddle and Julie Culley will run in the women's 5,000m at 3:05 p.m. ET.
(Not an American team member, but a man who has captured the hearts of many Americans, "Blade Runner" Oscar Pistorius will run for South Africa in the men's 4 x 400 relay at 4:20 p.m. ET.)
At the Aquatic Centre, divers Nick McCrory and David Boudia, who took bronze together in the 10m synchronized, compete in the individual 10m platform at 2 p.m. ET.
Freestyle wrestler Jordan Burroughs, a two-time NCAA champion and defending world champion, is the favorite in the 74 kg weight class.
The men’s basketball team continues its march to gold with a 4 p.m. ET semifinal game against Argentina.
America’s success in London so far is largely due to its dominance in the Aquatic Centre. The 2012 games’ five top medal winners are all U.S. swimmers, led by Michael Phelps, whose record career medal haul included four golds and two silvers in London. Teenage phenom Missy Franklin is in second place, with four golds and one bronze.
The top Chinese medalist is swimmer Sun Yang, with two golds, a silver and a bronze.
The top non-swimmer on the list is another American, gymnast Aly Raisman, whose two golds and a bronze places her 12th overall.
The team results largely match projections by Colorado College economist Dan Johnson, who uses a formula that takes into account countries’ wealth, population, and whether they’ve recently hosted the games.
China which hosted the Olympics in 2008, lost the total medal count to the Americans that year, 110 to 100, but won many more gold medals – 51 to America’s 36.
Johnson’s most recent model forecasted that the United States would win the total- and gold-medal count in 2012, followed by China, then Russia, then Great Britain.
He says he makes the predictions to put the medal count in context, allowing spectators to compare nations against statistics-based presumptions.
“It’s not about the count but how well your country performed against the expectation of what they should have done,” Johnson said in an interview before the Olympics.
He relishes the anomalies, like Kazakhstan, which has just as many gold medals -- but far fewer total medals – as Australia.
“It’s very fun to say we’re number one. But we should be number one," Johnson said. "It would be embarrassing if we weren’t number one, and to put us in a count against Romania is kind of ridiculous.”
For a full local listing of events being shown all day on NBC, the NBC Sports Network, Bravo, CNBC, MSNBC, the NBC Olympic Soccer Channel, the NBC Basketball Channel and Telemundo, please see NBCOlympics.com, where you can also find listings for all livestreamed events.