interest or use it to secure a mortgage loan. This picture of "complete ownership" is, of course, complicated by the obligation in most places to pay a property tax and by the fact that if the land is mortgaged, there will be a claim on it in the form of a lien. In modern societies, this is the most common form of land ownership. Land can also be owned by more than one party and there are various concurrent estate rules. Native title In Australia, native title is a common law concept that recognizes that some indigenous people have certain land rights that derive from their traditional laws and customs. Native title can co-exist with non-indigenous proprietary rights and in some cases different indigenous groups can exercise their native title over the same land. There are approximately 160 registered determinations of native title, spanning some 16% of Australia's land mass. The case of Mabo overturned the decision in Milirrpum and repudiated the notion of terra nullius. Subsequent Parliamentary Acts passed recognised the existence of this common law doctrine. Life estate Under common law, Life estate is an interest in real property that ends at death. The holder has the use of the land for life, but typically no ability to transfer that interest or to use it to secure a mortgage loan. Fee tail Under common law, fee tail is hereditary, non-transferable ownership of real property. A similar concept, the legitime, exists in civil and Roman law; the legitime limits the extent to which one may disinherit an heir. Leasehold Under both common law and civil law, land may be leased or rented by its owner to another party. A wide range of arrangements are possible, ranging from very short terms to the 99-year leases common in the United Kingdom, and allowing various degrees of freedom in the use of the property. Common land Rights to use a common may include such rights as the use of a road or the right to graze one's animals on commonly owned land. Sharecropping When sharecropping, one has use of agricultural land owned by another person in exchange for a share of the resulting crop or livestock. Easement Easements allow one to make certain specific uses of land owned by someone else. The most classic easement is right-of-way, but it could also include (for example) the right to run an electrical power line