But all countries state in advance that they have no obligation to accept any kind of offer - even if it is the cheapest. This is a needed provision: the cheapest is not necessarily the best. The cheapest offer could be coming from a very unreliable supplier with a bad past performance or a criminal record or from a supplier who offers goods of shoddy quality. The tendering policy of most of the countries in the world also incorporates a second principle: that of "minimum size". The cost of running a tender is prohibitive in the cases of purchases in small amounts. Even if there is corruption in such purchases it is bound to cause less damage to the public purse than the costs of the tender, which is supposed to prevent it! So, in most countries, small purchases can be authorized by government officials - larger amounts go through a tedious, multi-phase tendering process. Public competitive bidding is not corruption-proof: many times officials and bidders collude and conspire to award the contract against bribes and other, non-cash, benefits. But we still know of no better way to minimize the effects of human greed. Procurement policies, procedures and tenders are supervised by state auditing authorities. The most famous is, probably, the General Accounting Office, known by its acronym: the GAO. It is an unrelenting, very thorough and dangerous watchdog of the administration. It is considered to be highly effective in reducing procurement - related irregularities and crimes. Another such institution is the Israeli State Reviser. What is common to both these organs of the state is that they have very broad authority. They possess (by law) judicial and criminal prosecution powers and they exercise it without any hesitation. They have the legal obligation to review the operations and financial transactions of all the other organs of the executive branch. Their teams select, each year, the organs to be reviewed and audited. They collect all pertinent documents and correspondence. They cross the information that they receive from elsewhere. They ask very embarrassing questions and they do it under the threat of perjury prosecutions. They summon witnesses and they publish damning reports, which, in many cases, lead to criminal prosecutions.