世界贸易在2014年继续以缓慢的步伐增长，估计增长率为3.3%，略高于2013年，但明显远低于全球金融危机前二十年的长期趋势。在全球金融危机爆发之前的二十年中，世界贸易平均年度增长率是同期世界生产总值增长率的两倍以上。全球金融危机在2008年爆发，并引发了2009年的“大衰退”，导致世界贸易在2009年暴跌11%，其跌幅是世界生产总值衰退幅度的5倍。 之后， 除了在2010年有强劲反弹，世界贸易一直处在低迷增长，其增长率仅大约于世界生产总值增长率相当。联合国最新预测世界贸易增长将在今后两年有所改善（参见http://www.un.org/en/development/desa/policy/wesp/wesp_archive/2015wesp_chap1.pdf），但世界贸易增长与世界生产总值增长之间的比率仍将只有1.5比1，无法完全恢复到全球金融危机之前的趋势。
关键的问题是，全球金融危机之后世界贸易增长相对世界生产总值增长放缓除了周期性变化之外是否反映了全球经济和贸易发生了结构性变化。
其中肯定有周期性因素。例如，主要发达国家复苏乏力，特别是欧元区一直在衰退边缘徘徊，导致进口需求疲软。欧洲的进口需求目前仍然低于其在2008年水平的7％。发达国家需求不足直接影响世界贸易。从中期来看，发达国家进口疲软的趋势恐怕很难扭转，其中不少发达国家平均工资增长缓慢，甚至停滞，再加上人口老龄化，将一直会对进口增长产生下行压力。
再如，由于全球金融危机的爆发，许多国家推出了一些在世界贸易组织框架允许范围的临时性国际贸易和国际投资保护主义措施，限制了贸易流动。其中，20国集团成员国自2008年以来通过了一千多项贸易保护措施， 至2014年只取消了二百多项。 这些保护主义措施对世界贸易的限制还在不断积累。
然而，世界贸易增长和世界生产总值增长之间的关系的确也发生了一些结构性变化。
世界贸易增长可以持续不断地高于世界生产总值增长，其前提条件是国际贸易中商品和服务的价格相对各国国内贸易中商品和服务的价格呈不断下降趋势。而促成这种相对价格不断下降的因素包括：技术进步不断降低国际运输成本；新的贸易协定减少关税和其它贸易壁垒。回顾1990年代和2000年代，世界贸易增长之所以能够以2：1以上的比例高于世界生产总值增长的确受益于这些因素。例如，关贸总协定多边贸易谈判乌拉圭回合取得的成果;苏联解体后转型经济体国家，中国以及其他发展中国家逐步融入全球经济一体化，减少了国际贸易和投资壁垒，特别是中国加入世贸组织前后过程中对世界贸易的推动；欧盟，尤其是欧元区货币一体化，降低了贸易成本，不但促进了欧洲各国之间的贸易，也促进了欧洲与其他地区的贸易；信息和通信技术革命降低了贸易成本;全球价值链的形成和不断扩大，将制造业生产流程分解成不同的阶段，再分布不同的国家，同样促进了国际贸易。这些因素都导致了国际贸易的增长快于各国国内生产总值的增长，从而在全球范围内，世界贸易增长比世界生产总值增长高出两倍以上。
上述这些曾经在全球金融危机爆发之前驱动世界贸易强劲增长的因素似乎都已经结束了它们的使命。例如，世界贸易组织多哈回合多边贸易谈判在过去14年进展甚微，未能给国际贸易提供新的动力。有些分析人士可能会有疑义：多哈回合自2001年以来一直处于僵局，但为什么世界贸易直到金融危机爆发的2008年仍然能够保持高速增长？这是因为世界贸易直到2008年仍然继续受益于早期贸易自由化带来的滞后效应。例如，尽管中国加入世界贸易组织发生在2001年，但中国在2001年之后仍然有五年的宽限期逐步取消或降低了大量的贸易壁垒，继续促进国际贸易。目前，多哈回合之前贸易协定对国际贸易的增速作用已基本消失。虽然各种区域贸易协定仍然可以促进一些地区贸易，但区域贸易协定对世界贸易的长远和整体效果并不确定，无法取代世界多边贸易协定的作用。
同时，中国，以及前苏联和中、东欧转型经济体国家融入全球经济的过程经过二十多年的加速阶段之后，可能已经达到稳定状态。很显然，中国对外贸易经过二十年多年平均20%以上高速增长之后，中国在全球贸易中的份额已经从微不足道增加到12%，成为世界第一贸易大国。 然而，随着工资明显增长，劳动力从农业部门向制造业部门转移过程的逐步完成，以及与工业化相关的环境成本上升，预计中国出口增长不会再以20%速度增长。当然，从乐观的角度来看，其它一些发展中国家，特别是非洲，仍然可以在未来的一、二十年里给世界贸易带来新的动力，但恐怕很难达到中国在过去二十年的速度和规模。
因此，即使世界贸易增长有可能从过去几年的低迷中有所恢复，也很难重现金融危机之前二十年世界贸易的强劲增长。世界贸易增长与世界总产值增长之间的关系或许进入了新常态。
English summary
World trade flows continued to grow at a slow pacein 2014, expanding at about 3.3 per cent, slightly faster than in 2013but still well below the long-term trend of thedecades before the global financial crisis. In the two decadesprior to the global financial crisis, for instance, the annualgrowth of world trade, measured by imports in volume, was onaverage twice the growth of world gross product (WGP. The eruptionof the global financial crisis in 2008 and the subsequent GreatRecession in 2009 led to a collapse in world trade flows. In therecovery, except for a strong rebound in 2010, world trade has beenexpanding at a sluggish pace, only at about the same rate as worldgross product. In the forecast period, trade growth is expected toexpand moderately, but the ratio between the growth of world tradeand that of WGP will still not recover to the pre-crisistrend.
At issue is whether the slowdown in trade growthrelative to WGP in the past few years after the global financialcrisis reflects a fundamental change in the structure of the globaleconomy, or a transient and cyclical change in the relationshipbetween trade and GDP.
Among the cyclical changes, the anaemic recoveryin major developed countries, particularly the protracted recessionin the euro area, has led to feeble import demand.In the medium term, stagnant wage growthin many developed countries coupled with aging populations couldput further downward pressure on import growth.
Since the eruption of the global financial crisis,a large number of countries adopted temporary protectionistmeasures on international trade and investment, restricting tradeflows. It remains of concern that the overall trade restrictivenessof these measures continue to accumulate.
However, some changes in the relationship betweentrade growth and WGP growth may be structural.
World trade can grow faster than WGP for asustained period only if the prices of international goods andservices continue to decline relative to the prices of domesticgoods and services. These relative price declines can occur throughsuch factors as new trade agreements to reduce tariffs and othertrade barriers, and technological innovations to lower the costs ofinternational transportation.
The strong trade growth relative to WGP in the1990s and 2000s was indeed supported by these factors. For theexample, the achievements of the Uruguay Round of multilateraltrade negotiations in the GATT; the economic integration of theeconomies in transition, China and other developing economies intothe global economy, which removed and reduced barriers tointernational trade and investment, as exemplified in the processof China’s accession to the WTO; the increased trade and monetaryintegration in the European Union, especially the adoption of theeuro for a growing number of countries in the region; the reductionof transportation costs by the revolution in information andcommunication technology and other technologies; and the formationand increasing expansion of global value chains, which distributedvarious stages of production to different countries, all havesignificantly promoted international trade. This led to a muchfaster growth of trade flows in many countries relative to growthof their GDP and, at the global level, the growth of world trade attwice as the rate of WGP.
Some of these key factors that were driving worldtrade on a rapid track before the global financial crisis may haverun their course. For example, the WTO Doha Round of multilateraltrade negotiations has made little progress in the past fourteenyears, failing to provide new impetus to trade growth.
The proliferation of various regional tradeagreements (RTAs) may generate some new trade flows in someregions, but the overall effects of RTAs on the world trade in thelong run are not certain and cannot replace the role of themultilateral trading system (see the section on trade policybelow).
The integration process of the economies intransition and China into the global economy, after a phase ofacceleration in the 1990s and 2000s, may also have reached a steadystate. On the positive side, the rise of the African economies canprovide a renewed impetus to the world trade in the next decades,but it will take some time to see the results in largescale.
In short, growth of world trade is projected topick up some momentum from the subdued pace of the past few yearsin the aftermath of the financial crisis, but its dynamism aswitnessed in the two decades before the crisis may not come backsoon.