Only some three per cent of the land of Papua New Guinea is alienated; it is privately held under 99 year State Lease, or it is held by the State. There is virtually no freehold title; the few existing freeholds are automatically converted to State Lease when they are transferred between vendor and purchaser. Unalienated land is owned under customary title by traditional landowners. The precise nature of the seisin varies from one culture to another, but generally title is communal and in the hands of traditional clans. This is a matter of vital importance because a problem of economic development is identifying who the membership of customary landowning groups is, and thus who the owners are. Disputes between mining and forestry companies and landowner groups often devolve on the issue of whether the companies entered into contractual relations for the use of land with the true owners. Customary property — usually land — cannot be devised by will; it can only be inherited according to the custom of the deceased's people.