The Kingdom of Saudi Arabia is a country situated in Southwest Asia, the largest country of Arabia, by the Arabian Peninsula, bordering the Persian Gulf and the Red Sea, north of Yemen. Its extensive coastlines on the Persian Gulf and Red Sea provide great leverage on shipping (especially crude oil) through the Persian Gulf and the Suez Canal. The kingdom occupies 80% of the Arabian Peninsula. Most of the country's boundaries with the United Arab Emirates (UAE), Oman, and the Republic of Yemen (formerly two separate countries: the Yemen Arab Republic or North Yemen; and the People's Democratic Republic of Yemen or South Yemen) are undefined, so the exact size of the country remains unknown. The Saudi government estimate is at 2,217,949 square kilometres, while other reputable estimates vary between 2,149,690 and 2,240,000 sq. kilometres. Less than 1% of the total area is suitable for cultivation, and in the early 1960s, population distribution varied greatly among the towns of the eastern and western coastal areas, the densely populated interior oases, and the vast, almost empty deserts.