The relationship between Australia and New Zealand is exceptionally close on both the national and interpersonal scales. This close relationship goes back to the time of the first World War and the ANZAC Spirit forged at Gallipoli. Former New Zealand Prime Minister Mike Moore declared that Australians and New Zealanders have more in common than New Yorkers and Californians. Relations are especially close given the number of tourists that travel between the two countries and the (generally) common economic policies. Immigration, employment, and residency policies are also very liberal and generous between citizens of either nation, similar to a two-nation model European Union. Relations between Australia and New Zealand are similar to that of other neighbouring countries with a shared British colonial heritage, such as Canada and the United States. Some have defined the relationship as less one of friendship than of brotherhood, beset by sibling rivalry. Trans-Tasman relations is often used as a shorthand expression for the relationship between the two countries, since they are separated by the Tasman Sea.