Apparently all it takes is a coffee.

The LIBOR rate, or London Interbank Overnight Rate, is an index of the estimated interest rate commercial banks have to pay to borrow money short-term. It is based on estimates submitted by banks, rather than an actual market rate. It was recently revealed, mostly by Barclays, that over the past half decade the index estimates have been manipulated to benefit the banks that submit them. This has implications for consumers broadly, as many interest rates are indexed to the LIBOR, and similar indexes for other regions like the EURIBOR; for example, interest rates on adjustable rate mortgages are often defined as a base rate plus the LIBOR rate. 

A 20-year-old recently became internet famous for punching a
man who joked about raping a drunk girl on the street one
night.

When is it ethical--and more importantly, efficient--  for individuals to take justice into their own hands? This question is particularly salient in Ghana, where vigilante justice is a common response to crime, and that justics goes up to and includes death for perpetrators of rape or severe property crime.

Justice generally serves two economic purposes: to make an injured party whole, and to provide a disincentive against bad behavior. Vigilante justice tends to be focused on the latter. If you doubt this, just wait for the next Batman movie-- I guarantee my dear Bruce Wayne will wreak more economic havoc as the caped crusader than he will provide in redress. Vigilante justice comes at a high price, to the executioner, society, and to innocent parties who fall mistakenly fall victim to it, and is limited in the benefits it can provide. 

In order to be justified then, vigilante justice must have a very high deterrent benefit. This will generally only be the case when legal justice systems completely fail to act as deterrents to morally reprehensible acts.

It seems to me that the woman's decision to punch the rape joker fits this criteria. No court in the United States would ever provide any kind of consequence for comments like this man made. To me, the welfare gain from the chilling effect (amplified by publicity) this will have on such jokes, which quickly turn a fun night out into a stomah-clenching affair that can haunt a woman for months (if not years), clearly outweigh one guy having a sore nose for a couple weeks. 

Similarly, in Ghana, legal remedies are a poor deterrent to crime. (Especially legal remedies that are actually legal, NOT including police beating suspsects.) Even in clear cases where suspects are caught red-handed with eyewitnesses present, criminals often walk free. Two friends of mine were beaten with bricks a couple years ago, and one of the assailants was captured at the scene of the crime, but was released after several months of courtroom circus.  Death by beating, however horrific, not only provides a clear disincentive to crime but permanently removes a criminal from society.

So can vigilante justice be morally and efficiently right? Yes. Does that mean it should go unpunished? No. The fact that vigilante justice can have a high cost for falsely accused victims means that executioners must have a disincentive to engage in vigilante justice unless they are sure of its benefitcs. Punishing, or potentially punishing, perpetrators of vigilante justice provides that disincentive. So the woman who punched the joker should be potentially liable for damages, and those who engage in mob justice beyond that necessary for defense should be liable under assault laws, to prevent vigilantes from risking targeting those not truly guilty. 

This may seem like a rather extreme position; it is certainly influenced by living in situations where law enforcement seems ineffectual. However, the truth is, society engages in vigilante justice all the time. In the U.S., however, it is usually psychological, not physical: when someone cuts in line, they are often shamed, but not punched. Vigilante justice is an appropriate response to those inevitable situations where the law has no reach, but how it is exercised must be limited by disincentives against its most extreme forms.