The full cost of bringing a new drug (i.e. a drug that is a new chemical entity) to market — from discovery through clinical trials to approval — is complex and controversial. One element of the complexity is that the much-publicized final numbers often do not include just the simple out-of-pocket expenses, but also include «capital costs», which are included to take into account the long time period (often at least ten years) during which the out-of-pocket costs are expended; additionally it is often not stated whether a given figure includes the capitalized cost or comprises only out-of-pocket expenses. Another element of complexity is that all estimates are based on confidential information owned by drug companies, released by them voluntarily. There is currently no way to validate these numbers. The numbers are controversial, as drug companies use them to justify the prices of their drugs and various advocates for lower drug prices have challenged them. The controversy is not only between «high» and «low» — the numbers also vary greatly at the high end.