Transportation accounts for 10 to 30 percent of the cost of the LNG value chain. Carrier ships often are owned by LNG producers, but also sometimes are built as independent investments separate from specific LNG projects. The evolution of LNG transport ships has been dramatic. While the first LNG carrier was a converted freighter with aluminum tanks insulated with balsa wood, modern LNG carriers are sophisticated doublehulled ships specifically designed for the safe and efficient transportation of cryogenic liquid. In May 2005, 181 LNG carriers were operating, with another 74 under construction for delivery in the 2005-07 time frame.