Cruising has become a major part of the tourism industry, accounting for U.S.$29.4 billion with over 19 million passengers carried worldwide. The industry's rapid growth has seen nine or more newly built ships catering to a North American clientele added every year since 2001, as well as others servicing European clientele. Smaller markets, such as the Asia-Pacific region, are generally serviced by older ships. A cruise ship or cruise liner is a passenger ship used for pleasure voyages, where the voyage itself and the ship's amenities are a part of the experience, as well as the different destinations along the way. Transportation is not the prime purpose, as cruise ships operate mostly on routes that return passengers to their originating port, so the ports of call are usually in a specified region of a continent. There are even "cruises to nowhere" or "nowhere voyages" where the ship makes 2-3 day round trips without any ports of call. By contrast, dedicated transport oriented ocean liners do "line voyages" and typically transport passengers from one point to another, rather than on round trips. Traditionally, an ocean liner for the transoceanic trade will be built to a higher standard than a typical cruise ship, including high freeboard and stronger plating to withstand rough seas and adverse conditions encountered in the open ocean, such as the North Atlantic. Ocean liners also usually have larger capacities for fuel, victuals, and other stores for consumption on long voyages, compared to dedicated cruise ships.