The rest are a mix of opposition activists, evangelical Christians escaping religious persecution, and ethnic Kunama accused by Eritrea of siding with Ethiopia during the last war.
The camp, which lies amid rocky mountains about 60 km (37 miles) from the border and can only reached by one rough road, is overwhelmingly young and male.
In the heat of the afternoon, residents half-heartedly play table football or pool, chew narcotic khat leaves, or sleep.
Eyob Awok, a coordinator for the Ethiopian government agency responsible for refugees, says some 90 percent of the population are under 35 years old, and only 24 percent are women.
"SEX FOR SHELTER"
"Life is harsh for women," one 22-year-old resident, Miraf Gebremikael, tells Reuters. "Most are dependant on men, and because they have nothing they exchange sex for shelter."
Competition for water and firewood is also stoking tensions with local communities.
At one cafe, former soldiers and students sit discussing the dire relations between Ethiopia and their homeland, and their desperate lives in the camp.
Pinned to a wall behind them, a colour photograph displays a full continental breakfast on a table overlooking a beach on the French Riviera. But meals are much simpler in Shimelba.
The men say their food rations are too small, they are given no money for clothes or shoes, there is no doctor, and new arrivals are given no shelter and must hope other refugees offer them somewhere to sleep.
Ilunga Nganda of the U.N. refugee agency UNHCR -- which funds the camp -- blames limited resources.
"I understand their frustration," he says.
Many at the cafe say they hope to travel to Sudan, which lets registered refugees work, unlike Ethiopia which does not.
"In Ethiopia we are just prisoners," says Solomon, 28. "People are committing suicide here. Living under the Eritrean dictatorship was hell. And so is this camp."
One ex-soldier says he has heard that his family back in Eritrea were fined 50,000 nakfa (about $3,300) because he fled.
Others around him say the same fate befell their relatives.
"My mother, father and sister were jailed because they couldn't afford to pay," the man says. "I don't rest from thinking about them day and night."
