经济学人下载:犯罪余震

Science and technology
科学与技术

Policing
治安

The aftershocks of crime
犯罪余震

An idea borrowed from seismology may help to predict criminal activity.
从地震学上获取的灵感或许能预测犯罪行为。

LOS ANGELES is one of the most under-policed cities in America.
洛杉矶是美国警力最不足的城市之一，

With a mere 26 officers for every 10,000 residents, the Los Angeles Police Department needs all the help it can get.
每一万个市民只分配了26名警察，因此洛杉矶警局急需各方支援。

That help may be at hand, with a modification of technology used to predict another type of threat that the city is prone to: the aftershocks from earthquakes. Big earthquakes are uNPRedictable.
支援也许就近在咫尺，只要将一项技术修改一下便可。这项技术原本是用来预测余震的—这个城市很容易受到的另一种灾难。

Once they have happened, however, they are usually followed by further tremors, and the pattern of these is tractable.
大地震是无法预测的，但是大地震发生后随之而来的余震模式却是可以掌控的。

George Mohler, a mathematician at Santa Clara University, in California, thinks something similar is true of crimes.
加利福尼亚州的圣克拉拉大学的数学家乔治·默赫勒认为，余震和犯罪有着相似之处。

There is often a pattern of “aftercrimes” in the wake of an initial one.
在初始犯罪后，常会尾随一种“犯罪后效应”模式。

The similarity with earthquakes intrigued him and he wondered if the mathematical formulas that seismologists employ to predict aftershocks were applicable to aftercrimes, too.
这种和地震的相似性激起了他的兴趣，于是他想，如果地震学家应用的预测余震的数学公式应用到犯罪后效应中，又会如何呢？

To test this idea, he and a team of researchers from the University of California, Los Angeles, adapted a computer program used by seismologists to calculate the likelihood of aftershocks.
为了测试这一想法，他和一队来自加利福尼亚大学的研究人员采用了一套地震学家用来计算余震可能性的电脑程序，

They then seeded it with actual LAPD data on 2,803 residential burglaries that occurred in an 18km-by-18km region of the San Fernando valley, one of the city’s largest districts, during 2004.
输入了2004年，在圣费尔南多谷中面积为18*18km2的区域里发生的2803起住宅爆窃案的警方数据。

Using the seismological algorithms, the computer calculated which city blocks were likely to experience the highest number of burglaries the next day, and thus which 5% of homes within the area were at particular risk of being broken into.
通过地震学的运算法则，电脑计算出了哪些街区在第二天可能会遭到大批盗窃，因此区域内5%的住宅都冒有很大被盗的风险。

In one test the program accurately identified a high-risk portion of the city in which, had it been adequately patrolled, police could have prevented a quarter of the burglaries that took place in the whole area that day.
在一项测试中，这个程序精确地辨识出了该市的一块高风险区，而如果巡逻充足，警方本可以在那一天阻止该地区四分之一的盗窃案。

In addition to modelling burglary, Dr Mohler examined three gang rivalries in Los Angeles, using data from 1999 to 2002, and discovered that similar patterns emerge from gang violence as retaliations typically occur within days—and metres—of an initial attack.
除了用盗窃案做模型，默赫勒用1999到2002年的数据，也检测了三起洛杉矶的帮派斗争，并发现了相同的模式：在最初的袭击之后，几天内会在邻近区域很典型地发生复仇暴力。

That, too, should help police deploy their limited resources more effectively.
这也能帮助警方更有效地部署有限的资源。

RoboCop move over, then. ComputerCop is coming.
机器战警已经过时，现在是电脑战警的时代了。