Cost contingency

When estimating the cost for a project, product or other item or investment, there is always uncertainty as to the precise content of all items in the estimate, how work will be performed, what work conditions will be like when the project is executed and so on. These uncertainties are risks to the project. Some refer to these risks as "known-unknowns" because the estimator is aware of them, and based on past experience, can even estimate their probable costs. The estimated costs of the known-unknowns is referred to by cost estimators as cost contingency.

Contingency "refers to costs that will probably occur based on past experience, but with some uncertainty regarding the amount. The term is not used as a catchall to cover ignorance. It is poor engineering and poor philosophy to make second-rate estimates and then try to satisfy them by using a large contingency account. The contingency allowance is designed to cover items of cost which are not known exactly at the time of the estimate but which will occur on a statistical basis."

The cost contingency which is included in a cost estimate, bid, or budget may be classified as to its general purpose, that is what it is intended to provide for. For a class 1 construction cost estimate, usually needed for a bid estimate, the contingency may be classified as an estimating and contracting contingency. This is intended to provide compensation for "estimating accuracy based on quantities assumed or measured, unanticipated market conditions, scheduling delays and acceleration issues, lack of bidding competition, subcontractor defaults, and interfacing omissions between various work categories." Additional classifications of contingency may be included at various stages of a project's life, including design contingency, or design definition contingency, or design growth contingency, and change order contingency (although these may be more properly called allowances).

AACE International, the Association for the Advancement of Cost Engineering, has defined contingency as "An amount added to an estimate to allow for items, conditions, or events for which the state, occurrence, or effect is uncertain and that experience shows will likely result, in aggregate, in additional costs. Typically estimated using statistical analysis or judgment based on past asset or project experience. Contingency usually excludes:

Some of the items, conditions, or events for which the state, occurrence, and/or effect is uncertain include, but are not limited to, planning and estimating errors and omissions, minor price fluctuations (other than general escalation), design developments and changes within the scope, and variations in market and environmental conditions. Contingency is generally included in most estimates, and is expected to be expended".

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Wikipedia