For the purposes of the PSC, it is assumed that the government is not capable of eliminating unsystematic risk through diversification (even though in theory individual taxpayers can do so). Consequently, the PSC financial model should account for the consequences of all risks in the project, whether systematic or unsystematic. Where a particular cost or revenue item may be volatile over time, or the potential variance is difficult to estimate, the expected value should include a contingency or "certainty equivalent" adjustment. This is particularly relevant for cashflows that are likely to be subject to significant systematic risk and cannot be estimated with a high degree of accuracy.