A price mechanism or market-based method is any of a wide variety of ways to match up offers and requests that market players bid and ask:

• a bid is an offer to pay a fixed amount that is held open for a period of time
• an ask is an offer to sell for a fixed amount that is held open for a period of time

If the terms "pay" and "sell" are understood very generally, then, a very broad range of applications and different market systems can be enabled this way. Internet dating for instance could be based on offers to talk for a period of time, accepted by those who are compensated not in money but in additional credits to keep using the system. Or, a political party could trade support for different measures in a platform, perhaps using allocation voting to "bid" a certain amount of support for a measure that a leader has "asked" them to support: if the measure has enough support in the party, the leader will proceed - a very explicit model of so-called "political capital". A market system is any systematic process enabling many market players to bid and ask: helping bidders and sellers interact and make deals. ... A Net dating service is an example of a dating system. ... A political party is a political organization that subscribes to a certain ideology and seeks to attain political power within a government. ... Allocation voting is any voting system in which voters are assigned a number of points or other unit of account, and are expected to allocate these among a number of alternatives. ... This article concerns places that serve as centers of government and politics. ...

The main advantage of such methods is that conditions are laid out in advance and transactions can proceed with no further permission or authorization from any participant. When any bid and ask pair are compatible, a transaction occurs, in most cases automatically.

Though there are many concerns about liquidating any given transaction, even in a conventional market, there are ideologies which hold that the risks are outweighed by the efficient rendezvous. In greenhouse gas emissions trading this is particularly non-controversial as the whole atmosphere of Earth can reasonably be seen as one uniform body affected almost equally by emissions anywhere on Earth. There are thus almost no local effects, and only a measurable and widely agreed climate change effect, of a greenhouse gas emission, justifying a "cap and trade" approach. Somewhat more controversially the approach was applied even earlier to sulphur dioxide emissions in the United States, and was quite successful in reducing overall smog output there. A market is a mechanism which allows people to trade, normally governed by the theory of supply and demand, so allocating resources through the price mechanism. ... Increasing CO2 levels Greenhouse gases (GHG) are gaseous components of the atmosphere that contribute to the greenhouse effect. ... Emissions trading is a proposed economic solution to air pollution. ... Atmosphere may refer to: a celestial body atmosphere, e. ... The term climate change is used to refer to changes in the Earths climate. ... Emissions trading is a proposed economic solution to air pollution. ... Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ... Victorian-era London was notorious for its thick smogs, or pea-soupers, a fact that is often recreated to add an air of mystery to a period costume drama. ...

In most applications of such methods, however, the comprehensive outcome of the transaction is not so easily measured or universally agreed. Some theorists assert that, with appropriate controls, a market mechanism can replace a hierarchy, even a command hierarchy, by ordering actions for which the highest bid is received: In economics, a comprehensive outcome is the entire result of an event or process. ... A hierarchy (in Greek hieros, sacred, and arkho, rule) is a system of ranking and organizing things. ... A command hierarchy is a group of people committed to carrying out orders from the top, that is, of authority. ...

An infamous example is the assassination market proposed by Tim May, which were effectively bets on someone's death. This has since been generalized into the prediction market idea which the Pentagon proposed to operate as part of Total Information Awareness - however this proved controversial as it would theoretically let assassins predict and then benefit from their predictions, which they would cause to come true. This is however a problem even with the commodity markets and any other financial markets where a single person's choices or fate might be influenced, predicted, or decided by someone already in the market. An assassination market is a (theoretical) market wherein any party can place a bet (using anonymous electronic money, and pseudonymous remailers) on the date of death of a given individual, and collect a payoff if they guess the date accurately. ... Also known as information markets, idea futures, and virtual stock markets. ... In geometry, a pentagon is any five-sided polygon. ... The Information Awareness Office is a branch of the United States Department of Defenses Defense Advanced Research Projects Agency. ... Jack Ruby murdered the assassin, Lee Harvey Oswald, in a very public manner. ... Chicago Board of Trade Commodity market Commodity markets Commodity Markets are markets where raw or primary products are exchanged. ... The financial markets are markets which facilitate the raising of funds or the investment of assets, depending on viewpoint. ...

Less controversial applications of bid and ask matching include:

• industrial process control
• various applications in social networks (including dating above)
• a wiki "revert currency
• calculating interest in court judgments or homestead credit
• determining which of several assets in a divorce are most prized by each party, and accordingly, who should receive what for maximum amiability and minimum capital asset sale and lifestyle disruption