2016 经济学人补充译文 19

 昵称dc3es 2016-06-23


Free exchange

A fare shake

Jacking up prices may not be the only way to balance supply and demand for taxis



IT IS a familiar ritual for many: after a late night out you reach for your smartphone to hail an Uber home, only to find—disaster—that the fare will be three times the normal rate. Like many things beloved by economists, “surge pricing” of the sort that occasionally afflicts Uber-users is both efficient and deeply unpopular. From a consumer’s perspective, surge pricing is annoying at best and downright offensive when applied during emergencies. Extreme fare surges often lead to outpourings of public criticism: when a snowstorm paralysed New York in 2013, celebrities, including Salman Rushdie, took to social media to rail against triple-digit fares for relatively short rides. Some city governments have banned the practice altogether: Delhi’s did so in April.很多人都很熟悉这样的情形:外出玩乐至深夜的你拿出智能手机,打算叫一辆优步(Uber)车回家,结果发现——见鬼,车费要比平常贵三倍。如同经济学家们所钟爱的很多事物一样,这种偶尔会让优步用户们饱受困扰的“高峰期定价”行之有效,却十分不受人待见。从消费者的角度讲,高峰期定价至少有些讨厌,但要在有急事时碰到就着实让人光火了。车费涨得太高往往会导致群情激愤。2013年,纽约在一场暴雪后陷入瘫痪,一段并不算长的路程,车费却要高达上百美元。包括萨尔曼·拉什迪(Salman Rushdie,译注:印度裔英国作家)在内的名人们通过社交媒体痛斥这种情况。有些城市的政府索性禁止此类涨价行为——德里已经于四月开始实行。

Uber is sticking with surge pricing for now, but Jeff Schneider, one of its machine-learning experts, recently suggested that the company is interested in developing systems that rely on technology, rather than price, to allocate cars. Even if such a technological fix proves elusive, however, local governments do not need to regulate or ban surge pricing to reduce its sting.

Surge (or dynamic) pricing relies on frequent price adjustments to match supply and demand. Such systems are sometimes used to set motorway tolls (which rise and fall with demand in an effort to keep traffic flowing), or to adjust the price of energy in electricity markets. A lower-tech version is common after natural disasters, when shopkeepers raise the price of necessities like bottled water and batteries as supplies run low. People understandably detest such practices. It offends the sensibilities of non-economists that the same journey should cost different amounts from one day or hour to the next—and more, invariably, when the need is most desperate.

目前优步仍执行着高峰期定价,但该公司一位机器学习专家杰夫·施耐德(Jeff Schneider)近日表示,公司有兴趣研发依靠技术而非价格来调配车辆的系统。然而,即使技术手段未能奏效,当地政府也没必要为了缓解小小的痛痒,就管控或叫停高峰期定价。


Yet surge fares also demonstrate the elegance with which prices moderate a marketplace. When demand in an area spikes and the waiting time for a car rises, surge pricing kicks in; users requesting cars are informed that the fare will be a multiple of the normal rate. As the multiple rises, the market goes to work. Higher fares ration available cars by willingness to pay: to richer users, in some cases, but also to those less able to wait out the surge period or with fewer good alternatives. Charging extra to those without good alternatives sounds like gouging, yet without surge pricing such riders would be less likely to get a ride at all, since there would be no incentive for all the other people requesting cars to drop out. Surge pricing also boosts supply, at least locally. The extra money is shared with drivers, who therefore have an incentive to travel to areas with high demand to help relieve the crush.然而,高峰期价格也展示了价格是如何轻巧自如地稳定市场的。当一个地区内需求激增、等车时间延长时,高峰期定价便会介入——叫车的用户会被告知,车费将会是平常的若干倍。随着车费成倍增长,市场开始起效。高额车费下会按照用户的支付意愿来调配空车:有时会分配给富有的用户,但也会分配给那些不能等高峰期结束,或没有多少其他更好选择的用户。向没有其他出行方式的人收取额外费用听着像在宰客,但要是没有高峰期定价,这些人就更难叫到车,因为其他叫车的人中不太会有人主动中途退出。另外,高峰期定价至少在局部地区刺激了供给。司机们能从多收取的车费中分得一杯羹,因而会有动力开往需求较高的区域以缓解用车压力。

A recent analysis published by Uber illustrates how the system is intended to work. Jonathan Hall, head of economic research at Uber, Cory Kendrick, a data scientist at the firm, and Chris Nosko, of the University of Chicago, compared two high-demand cases in New York city to illustrate how surge pricing is intended to work. In March 2015 it kicked in after a sold-out concert by Ariana Grande, a singer, in an arena in the middle of Manhattan. As the show came to an end, the number of people in the area opening the Uber app quadrupled in just a few minutes. Uber’s algorithm swiftly applied surge pricing; the average waiting time for a car rose only modestly, while the “completion rate”—the share of requests for rides that are met—never fell below 100%. On New Year’s Eve in 2014, in contrast, Uber’s surge-pricing algorithm broke down for 26 minutes, leaving New York without surge pricing. The average wait time for a car soared from about two minutes to roughly eight, while the completion rate dropped below 25% (see chart).优步最近发布的一项分析报告阐释了这种定价体系的运作机制。优步经济研究部门主管乔纳森·霍尔(Jonathan Hall)、优步数据科学家科里·肯德里克(Cory Kendrick)以及芝加哥大学的克里斯·诺斯科(Chris Nosko)对比了发生在纽约市区的两个高需求案例,来阐明高峰期定价如何运作。2015年3月,女歌手爱莉安娜·格兰德(Ariana Grande)在曼哈顿中部的一处场馆举办了一场爆满的演唱会,高峰期定价就起了作用。随着演出接近尾声,该地区打开优步应用的人数在短短几分钟内增长了四倍。优步的算法迅速启用了高峰期定价;平均等候时间只是稍有增加,而“成单率”——用车需求得到满足的比例——从未低于100%。与这个案例结果相反,2014年的跨年夜,优步的高峰期定价算法出现了26分钟的故障,致使纽约无法实行高峰期定价。结果平均等候时间从约两分钟猛增到近八分钟,成单率则降到了25%以下(见图表)。

The comparison may overstate the power of surge pricing. Even without the help of algorithms, cab drivers know to converge on a venue as an event finishes; more Uber drivers than normal were surely in the area at the end of Ms Grande’s concert in expectation of the extra business. Yet the possibility of earning a surge fare may also strengthen drivers’ incentives to anticipate and respond pre-emptively to high demand. Ironically, the better Uber’s surge-pricing algorithm works, the less the company will need to use it, since drivers’ pre-emptive responses will tend to eliminate the demand imbalances that make surge pricing necessary in the first place.

There are tantalising hints that Uber hopes to follow this logic to its conclusion. Mr Schneider noted that clever machine-learning tools could process Uber’s piles of data and determine when and where demand is likely to outstrip the supply of cars. There would be no need to wait until demand starts to rise, nor for drivers to scan concert schedules. The ability to anticipate demand would be of some use to Uber today: it could tell drivers where they are likely to be needed. But they would presumably not respond as rapidly as they do to the inducement of surge fares. Eventually, however, Uber hopes to replace its human drivers with autonomous vehicles, which could be directed around the city by the company’s computers without any pecuniary incentives. (The company still has an incentive to maximise earnings, though, so it might opt to keep surge pricing even if technology made it redundant, at the risk of further public rage.)这两个案例的对比可能夸大了高峰期定价的效力。即使没有算法的帮助,出租车司机们也知道在某项活动结束后聚集到主办地点附近等活。当然,格兰德的演唱会结束后,场外希望能多拉些活儿的优步司机肯定比平时要多。然而,在高额车费的激励下,司机们更有可能会预判高需求并提早响应。讽刺的是,优步高峰期定价的算法运行得越好,优步就越没必要使用它:因为如果司机提早做出了反应,供需失衡有可能会消除,这样一来就没有实施高峰期定价的必要了。


Apps and downs

Whether Uber remains a big part of the transport network in future, and whether it retains surge pricing, depends in part on how well local governments manage the transport system as a whole. In districts or cities where travellers have appealing alternatives, in the form of good public transport or private competitors to Uber, users will be more sensitive to price. Surge pricing will therefore not generate a big financial windfall for Uber (or its drivers). But where public transport is thin on the ground, or where Uber has little private competition, it is a different story. In other words, surge pricing is really only as painful as local officials allow it to be.



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