LONDON (Bloomberg) — Almost one in five of the world's capesize carriers is stuck in lines outside ports in China, Brazil and Australia, broker Simpson, Spence & Young Ltd. said.

There are 154 of the ships waiting to berth, about 100 more than in November, SSY said in a report last week. The cost of hiring a capesize, which can haul about 175,000 metric tons of coal and iron ore, has jumped 30 percent this month.

Iron ore is the biggest single dry bulk commodity hauled by sea, accounting for about 25 percent of the total this quarter, according to Drewry Shipping Consultants Ltd. in London. China, the world's biggest steel-producing nation, imported 57 million metric tons of iron ore in April, the most since at least 2004.

"The record levels of iron-ore volumes have continued to put pressure on China's port infrastructure," London-based SSY said in its report. With a "substantial" share of the fleet tied up in the Pacific, supply of the vessels in the Atlantic is "very tight," the broker said.

The Baltic Dry Index, a measure of commodity shipping costs, rose for a fifth day in London, taking its advance this year to 420 percent.