It is suggested that the present full rental value would be obtainable at the future date, as capital values are frequently calculated by use of values which are known at the date of valuation. Any possibility of further increases in rental value between the present and the future is reflected conventionally by the choice of a lower yield for the valuation of a property, signifying that the risk entailed in investing is reduced by the prospect of an enhanced future rental value. Most values change with time if there is inflation in an economy (particularly in property values), and it is often suggested that valuers should attempt to calculate what future rental values will be by considering trends in value, and that valuations should then be made utilising anticipated future rents. Valuations done on this basis became much more of a practice during the 1980s as changes in rental levels became quite substantial over relatively short periods of time. Some valuers therefore argue that it is unwise and impracticable to value without taking into account expected future increases in rental income, as to ignore such increases will result in the under-valuation of interests in property.