Investment in building construction represents the investment on any permanent structure with walls and a roof that provides protection and shelter from and for a social/physical environment for people/materials. Such structures also include the machinery and equipment component which forms a part of the structure with functions such as plumbing, electrical wiring, air conditioning or elevators. For example, building construction represents expenditures on aircraft hangars, factories, hospitals, hotels, office buildings, railway stations, schools and shopping centres. Investment in building construction is composed of three major components, often reffered to as ICI: Industrial; Commercial ; and Institutional and government building construction.