In economics, an externality is the cost or benefit that affects a third party who did not choose to incur that cost or benefit. Externalities occur when the production or consumption of a product or service's private price equilibrium cannot reflect the true costs or benefits of that product or service for society as a whole; this causes the externality competitive equilibrium to not be a Pareto optimality. Externalities can be either negative. Governments and institutions take actions to internalize externalities, thus market-priced transactions can incorporate all the benefits and costs associated with transactions between economic agents; the most common way this is done is by imposing taxes on the producers of this externality. This is done similar to a quote where there is no tax imposed and once the externality reaches a certain point there is a high tax imposed. However, since regulators do not always have all the information on the externality it can be difficult to impose the right tax.

Once the externality is internalized through imposing a tax the competitive equilibrium is now Pareto optimal. For example, manufacturing activities that cause air pollution impose health and clean-up costs on the whole society, whereas the neighbors of individuals who choose to fire-proof their homes may benefit from a reduced risk of a fire spreading to their own houses. If external costs exist, such as pollution, the producer may choose to produce more of the product than would be produced if the producer were required to pay all associated environmental costs; because responsibility or consequence for self-directed action lies outside the self, an element of externalization is involved. If there are external benefits, such as in public safety, less of the good may be produced than would be the case if the producer were to receive payment for the external benefits to others. For the purpose of these statements, overall cost and benefit to society is defined as the sum of the imputed monetary value of benefits and costs to all parties involved.

Two British economists are credited with having initiated the formal study of externalities, or "spillover effects": Henry Sidgwick is credited with first articulating, Arthur C. Pigou is credited with formalizing the concept of externalities. A negative externality is any difference between the private cost of an action or decision to an economic agent and the social cost. In simple terms, a negative externality is anything. An example is the toxic gases that are released from industries or mines, these gases cause harm to individuals within the surrounding area and have to bear a cost to get rid of that harm. Conversely, a positive externality is any difference between the private benefit of an action or decision to an economic agent and the social benefit. A positive externality is anything. For example, planting trees makes individuals' property look nicer and it cleans the surrounding areas. Suppose that there are K different possible allocations and N different agents, where K, N < ∞ and N ≥ 2.

Suppose that each agent has a type θ i ∼ F i and that each agent gets payoff v i + t i, where t i is the transfer paid by the i -th agent. A map f = is a social choice function if ∑ i = 1 N t i ≤ 0 for all θ ∈ N. An allocation κ: N → K is ex-post efficient if ∑ i = 1 N v i ≥ ∑ i = 1 N v i for all θ = ∈ N and all k ∈ K. Let κ ∗ denote an ex-post efficient allocation and let κ ~ i denote an ex-post efficient allocation without agent i; the externality imposed by agent i

Sam Fisher is a former professional Australian rules footballer who played for the St Kilda Football Club in the Australian Football League. Between the ages of 17 and 19 Fisher was a promising junior golfer and played off a handicap of 1, he won the Riverland Tyre and Mag Boxing Day Classic four times, twice with his father Terry and twice with his brother Ben. However, Fisher gave away a possible career in golf for AFL football. Fisher began playing Australian rules in South Australia with West Adelaide, where he was first identified by AFL scouts at the age of 21; the versatile defender was selected as pick number 55 in the 2003 AFL Draft. He made his debut in 2004 following some injuries to other key defenders In 2005, Fisher took a major step in his career and improved to hold down a regular spot in the Saints' defence, he played on the third best forward of the opposition and began to provide terrific run from the half-back line. In 2006 he had up 421 disposals for the season, his run and carry from the half-back line was critical to St Kilda's 6th-place finish and he finished third in the St Kilda best and fairest award.

Injuries to other key defenders at the start of the 2007 season saw Fisher assume the mantle at full-back. He performed against the power forwards of the competition before injuring his hamstring in Round 4, he returned in Round 7 and was able to resume his attacking position across halfback in the second half of the year. He finished off the year and was nominated in the backline in the squad of 40 players for the All-Australian Team. Fisher was ranked 17th in kicks per game and 2nd in marks per game. Fisher signed a two-year contract extension in September 2007 until the end of 2010. Fisher got more of a chance to play as a key position backman after a season-ending injury to Matt Maguire early in the season, he played in St Kilda’s 2008 NAB Cup winning side, the club's third pre-season cup win. Fisher had a strong season, averaging 22 disposals and 8 marks a game at the end of the regular season, he was included in the All-Australian team on the half-back flank, the first time he had been awarded that honour.

Fisher won the Saints Trevor Barker Award for the best and fairest player in the season. He polled 680 votes to finish ahead of Nick Riewoldt. Fisher again showed a strong presence in St Kilda's home and away season, playing as either a loose backman or the centre halfback, he performed in the first qualifying final against Collingwood with a career high 42 disposals. Fisher played in 21 of 22 matches in the 2009 home and away rounds in which St Kilda qualified in first position for the finals series, winning the club’s third minor premiership. St Kilda qualified for the 2009 AFL Grand Final after preliminary finals wins. Fisher played in the grand final. Fisher played 24 games in 2010, including four finals matches, he was one of St Kilda's best players in the drawn Grand Final, had 16 possessions in the Grand Final replay before injuring his hamstring before half time. As of the end of the 2010 season, Fisher had played in 12 finals matches including three grand finals. At the conclusion of the 2016 season, Fisher announced his retirement from AFL football, having played 228 games for St Kilda.

Sam Fisher's profile on the official website of the St Kilda Football Club Sam Fisher's playing statistics from AFL Tables

For the Toronto-based weekly see Eye Weekly. Eye magazine, the international review of graphic design, is a quarterly print magazine on graphic design and visual culture. First published in London in 1990, Eye was founded by Rick Poynor, a prolific writer on graphic design and visual communication. Poynor edited the first twenty-four issues. Max Bruinsma was the second editor, editing issues 25–32, before its current editor John L. Walters took over in 1999. Stephen Coates was art director for issues 1-26, Nick Bell was art director from issues 27-57, Simon Esterson has been art director since issue 58. Frequent contributors include Phil Baines, Steven Heller, Steve Hare, Richard Hollis, Robin Kinross, Jan Middendorp, J. Abbott Miller, John O’Reilly, Rick Poynor, Alice Twemlow, Kerry William Purcell, Steve Rigley, Adrian Shaughnessy, David Thompson, Christopher Wilson and many others. Other contributors have included Nick Bell, Gavin Bryars, Anne Burdick, Brendan Dawes, Simon Esterson, Malcolm Garrett, Anna Gerber, Jonathan Jones, Emily King, Ellen Lupton, Russell Mills, Quentin Newark, Tom Phillips, Robin Rimbaud, Stefan Sagmeister, Sue Steward, Erik Spiekermann, Teal Triggs, Val Williams and Judith Williamson.

The magazine has had five publishers: Wordsearch, Quantum Publishing, Haymarket Brand Media and Eye Magazine Ltd. formed in April 2008 after a management buyout. Communication Arts Emigre magazine Graphis Inc. Print Visible Language John L. Walters Eye, Nos. 1–12, edited by Rick Poynor, Wordsearch Ltd, London, 1991–1994. Eye, Nos. 13–17, edited by Rick Poynor, Emap Architecture, London, 1994–1995. Eye, Nos. 18–24, edited by Rick Poynor, Emap Construct, London, 1995–1997. Eye, No. 25, edited by Max Bruinsma, Emap Construct, London, 1997. Eye, Nos. 26–32, edited by Max Bruinsma, Quantum Publishing, London, 1997–1999. Eye, Nos. 33–55, edited by John L. Walters, Quantum Publishing, London, 1999–2005. Eye, Nos. 56–66, edited by John L. Walters, Haymarket Brand Media, London, 2005–2008. Eye, Nos. 67–97, edited by John L. Walters, Eye Magazine Ltd. London, 2008-2018. EyeMagazine.com Eye Magazine Blog