The Trade War and Macroeconomic Identities

To the surprise of most, consensus was readily reached on a truce at the recent tariff talks between China and the US in Geneva. For the time being, tariff rates have reverted to the levels prior to the so-called “Liberation Day”, though the international landscape can hardly return to its previous state. The US president…


To the surprise of most, consensus was readily reached on a truce at the recent tariff talks between China and the US in Geneva. For the time being, tariff rates have reverted to the levels prior to the so-called “Liberation Day”, though the international landscape can hardly return to its previous state. The US president Donald Trump has been manipulating “negotiation tactics”, with the asking price constantly fluctuating―now high, now low; now real, now fake. Both carrots and sticks are used to create more room for negotiation. Nevertheless, due to a lack of underlying strength and messy logic, the trade war resembles poorly-executed acrobatics on the part of the US, pushing the Global Economic Policy Uncertainty Index to a historical high (see Note 1).

After over a month of turmoil, Trump’s tariff myth has now been debunked. Despite his claim that tariffs would be paid by foreign countries, he demanded Walmart absorb the tariff-induced additional costs instead of passing them on to consumers, soon after the company notified its customers of the price increase. Despite his claim that tariffs will revitalize America’s manufacturing industry and create jobs, Trump criticized Apple CEO Tim Cook for moving the production of iPhones to India instead of relocating it to the US.

What is more, the sharp reactions from financial markets worldwide to both rising tariffs and temporary tariff pauses further highlight the negative economic impacts of America’s tariff sticks. The Trump team cannot help but retract their previous claims, admitting that tariffs do have short-term effects though they will ultimately do more good than harm to the country in the long run.

So far, apart from reaching an insubstantial agreement with the UK, the US has made little headway in its trade negotiations with other countries. The 90-day pause on the “reciprocal” tariffs is scheduled to end on 9 July 2025. Many countries are starting to see through America’s tough façade and have decided to observe how other nations fare to gauge America’s bottom line. Their hesitation to kowtow is becoming more and more embarrassing for the US. A few days ago, Trump and Treasury Secretary Scott Bessent said separately that America will unilaterally levy the “reciprocal” tariffs announced on “Liberation Day” on other countries if they show no interest in negotiating. This is an American modus operandi to browbeat other countries. Nonetheless, a solution will need to be found and there may be opportunities for breakthroughs in the coming weeks.

Misconception: imports curb domestic production

Trump and his cabinet must have their views and reasons, though not necessarily correct, to go to such lengths with their tariff weapon. They are even gambling with America’s economy and global image. Below is a discussion of this based on two macroeconomic identities 101.

America’s gross domestic product (GDP) figures for the first quarter of 2025 announced at the end of last month reveal a real growth rate decline of 0.3% on an annualized basis compared with the previous quarter. Public opinion in the US shows that this is the result of American businesses importing foreign products in bulk before Trump’s tariff hikes take effect. Mainstream media outlets, including The Wall Street Journal, The Washington Post, Bloomberg, and CNBC, have reported this view. The rationale is that imports have reduced domestic production.

By this logic, the huge amount of Chinese exports to the US over the decades has contributed significantly to a reduction in US production and economic growth while displacing American workers. One of the reasons why Trump has been elected as president twice is his ability to take advantage of this public sentiment, highlighting his commitment to using tariffs to resist foreign goods and protect the interests of America and its workers. His trade advisor Peter Navarro has echoed similar claims over the years.

It is, in fact, a misconception that imports will curb domestic production. Simply put, imports are “foreign production”, i.e. the volume of imports affects foreign rather than domestic production. This may not completely clear all doubts, so let us focus on the GDP.

Macroeconomics 101 textbooks usually explain how to measure GDP with the following equation: Y = C + I + G + EX – IM, where Y represents GDP, C stands for consumption, I represents real investment, G is government expenditure, EX denotes exports, and IM represents imports. More often than not, readers may mistakenly think that since IM is subtracted, an increase in IM will result in a corresponding decrease in Y. However, this equation is just an accounting identity. With production volume already fixed (e.g. GDP from the previous year), to find the total value, a simpler way is to calculate the sum of the components on the right side of the equation. To understand the relationship between imports or trade deficits and GDP, it is essential to look beyond this equation by incorporating hypotheses and analyses related to economic behaviours.

Imports, investment, and consumption cancelling each other out

Suppose that in anticipation of the tariff hikes, US companies import foreign goods in advance. Despite the increase in imports, this is not the only economic activity. If the imported goods are then stored in warehouses, in the above equation, corporate inventory investments (i.e. part of I) will accelerate with imports, thus cancelling each other out without changing Y (GDP). If the imported goods are immediately sold to consumers, that will be tantamount to a rise in consumption and, in the above equation, C and imports will go up simultaneously and cancel each other out.

Similarly, if the goods are imported by the government rather than by enterprises, there will be a corresponding surge in G.

In other words, the slight contraction of US GDP in the first quarter of 2025 has nothing to do with the increase in imports by American companies prior to the implementation of new tariffs, but is caused by other factors. By the same token, any change in the value of IM will generally result in corresponding change in C, I, or G but will not affect domestic production.

Assuming the demand for imports is to replace domestic products, this means local consumers will buy fewer local products and switch to foreign products instead, causing domestic production to fall. However, strictly speaking, import behaviour alone will not directly reduce domestic production. A cut in production only occurs when consumers stop buying local products for some reason. If the reason is that local products cannot compete with cheaper and better foreign goods, then cutting back on domestic production in uncompetitive sectors and enabling consumers to purchase more affordable imported goods could be a suitable approach. In so doing, freed-up resources may be reallocated to more competitive industries. In addition, imports and domestic production are not necessarily mutually exclusive. They can complement each other, particularly when importing parts, components, and raw materials is involved. In such cases, the greater the import volume, the higher the domestic production.

All in all, the relationship between import volume or trade deficits and GDP presents multiple possibilities. More imports do not invariably result in less domestic production. On the contrary, limiting imports by tariffs or other trade barriers does not necessarily benefit domestic production and may even backfire. In the past few years, while the US has seen continued growth of expanding imports, the country’s unemployment rate has remained at a historical low of 4% (with the exception of the period of the coronavirus pandemic). This contradicts the view that imports hinder domestic production.

No direct causal link between current account deficits and foreign capital inflows

Another macroeconomic identity misused by the Trump administration is the notion that current account deficits equal net inflows of foreign capital. The current account primarily consists of the trade balance. For the sake of simplicity, the minor parts are left out of consideration here. Foreign capital inflows refer to the use of foreign capital within a country, similar to loans provided by foreign entities for domestic purposes.

To explain why current account deficits are equivalent to inflows of foreign capital, consider the US as an illustrative example. The fact that the US runs up trade deficits, meaning that Americans consume more foreign goods than foreigners consume American products, implies that, regardless of transactions at the individual or corporate level, the additional foreign goods consumed by Americans are, in effect, provided on temporary loan to the US by foreign entities. The larger the trade deficit, the greater the debt the US owes other countries, or alternatively, the greater the inflow of foreign capital. The coexistence of these two phenomena represents the two sides of the same coin.

Even if the US prints more money to settle its trade deficits, this will still translate into debts owed to other countries. It is because US dollars function not only as liabilities of the Federal Reserve but also as assets for foreign holders. Nonetheless, the nominal return on cash holdings of US dollars is zero, in contrast to that generated by US dollar-denominated bonds.

The equivalence between a current account deficit and capital inflows is also an accounting identity. Although it does not represent any causal relationship, the Trump team insists on framing it as follows.

Since the greenback is the primary foreign exchange reserve currency, central banks around the world have been purchasing US dollars in foreign exchange markets, leading to an appreciation of the dollar against other currencies. As a result, on the one hand, America’s rising imports and declining exports have created a colossal long-term trade deficit, a contraction of manufacturing, higher unemployment among workers, and a reliance on foreign goods. On the other hand, foreign countries enjoy trade surpluses, which they convert into US government bonds through deployment of the US dollars earned. Expanding foreign holdings of US bonds would pose a threat to the dollar’s status as a reserve currency and to US national security.

In other words, the fact that foreign capital has been flowing into the US to acquire dollars and US treasury bonds, leading to a trade deficit and diminished domestic manufacturing, appears to support the claim that America provides the world with a reserve currency, only to end up shouldering economic losses. To “Make America Great Again” and to mitigate America’s “grievances”, Trump has dramatically raised tariffs on many trading partners and is toying with the idea of converting existing US Treasury bonds into 100-year, non-tradeable zero-coupon bonds.

However, these narratives simply do not tally with reality. First, the value of US treasury bonds held by foreign central banks hovered around US$4 trillion from 2012 to the end of 2024, and even showed signs of a slight decrease (see Note 2).

This indicates that, on the whole, foreign central banks have not increased their holdings of US treasury bonds as foreign reserves while America’s current account deficit has expanded substantially since 2020.

Furthermore, if the share of manufacturing employees among non-farm employees is used as an indicator of manufacturing’s importance to the American economy, this proportion has progressively fallen from 35% at the end of the Second World War to approximately 8% today (see Note 3). Yet, over the same period, the US dollar’s exchange rate has experienced multiple fluctuations. For example, the real effective exchange rate of the dollar drastically declined from 118 at the time of the signing of the Plaza Accord in 1985 to 90 a few years later. The rate remained low for several years, with no change in the speed or trend of the decline in the share of manufacturing employees.

It may well be that the economic narratives of politicians merely serve the purposes of influencing public opinion and serving political ends. Only four months into Trump’s second term, the logic underlying US economic policy is already riddled with contradictions and barely coherent. During the presidential campaign last year, voters generally regarded economic policy as Trump’s forte, but according to a recent Reuters survey, only 37% of respondents still have the same view. It seems likely that the Global Economic Policy Uncertainty Index will continue to fluctuate at high levels in the next few years.

Note 1: https://www.policyuncertainty.com/
Note 2: https://fred.stlouisfed.org/series/BOGZ1FL263061130Q
Note 3: https://fred.stlouisfed.org/graph/?g=cAYh

Translation
早前中美雙方在日內瓦就關稅會談,出乎意料地迅速達成休戰共識,關稅稅率暫時回落至所謂美國「解放日」之前的水平,但全球局面却難復舊觀。美國總統特朗普玩弄所謂談判技巧,叫價忽高忽低、忽真忽假,威逼利誘,爲己方製造談判空間。可是礙于底氣不足,邏輯紊亂,貿易戰猶如美方蹩脚的馬戲班雜耍,將全球經濟政策不確定性指數推至歷史高點【注1】。

經過一個多月的折騰,特朗普的關稅神話已不攻自破。說關稅是由外國而非美國支付,却在沃爾瑪通知消費者貨品因關稅而加價時,責成沃爾瑪應「吞下」關稅,而非轉嫁給消費者。說關稅會重振美國製造業和創造工作崗位,却批評蘋果公司首席執行官庫克將iPhone生産轉到印度,而非帶回美國。

至于金融市場對關稅上升或暫緩的大幅度反應,更是不留情面的表達關稅大棒對經濟的負面影響。特朗普團隊只能改變口風,說關稅畢竟有些短期影響,長遠來說還是對美國利多于弊。

目前,除了與英國達成沒太多實質內容的協議外,美國和其他國家的貿易談判還沒任何成果。對等關稅90天寬限期將在7月9日結束,大抵各國都認識到美國外强中乾,想多看其他國家的情况來判斷美國的底綫,沒快快下跪,這使美國的處境愈來愈尷尬,因此特朗普和財政部長貝桑都分別在數天前表示,若各國沒談判誠意,美國便會單方面徵收「解放日」當天宣布的對等關稅稅率。這是美國慣性的威嚇伎倆,惟事情畢竟要解决,也許在未來數周會出現一些突破口。
進口遏本地生産屬錯誤理解

特朗普和他的團隊把關稅鬧得這麽大,賭上美國的經濟和國際形象,自然有他們的看法和執念,雖然不一定都正確,這裏以兩條宏觀經濟學入門的恒等式來討論。

美國上月底公布本年首季GDP數字,實質增長率與前一季相比,以按年下跌0.3%的速度减少,大部分美國輿論都認爲是美國企業爭取在特朗普政府提高關稅之前,大量進口外國商品所致。衆多的主流傳媒,包括《華爾街日報》、《華盛頓郵報》、彭博、消費者新聞與商業頻道等,均如此報道。背後的思路,是進口降低了本地生産。

按這個邏輯推理,中國多年來對美國的大量出口,便嚴重地拉低美國的生産和經濟增長,同時奪去美國工人的就業機會。特朗普兩次當選總統,其中一原因是成功地利用這種思維,標榜自己會以關稅抗拒外國産品,保護美國和美國工人的利益。他的貿易顧問納瓦羅,也多年來不斷重複類似言論。

然而,進口會减少本地生産,是錯誤的理解,因爲進口是「外國的生産」,進口多少,影響的是外國而非本地生産。這或許不能完全澄清所有疑慮,那看看本地生産總值,也就是所謂GDP。

宏觀經濟學入門教科書,通常都會在首一、二章解釋GDP的量度方法,幷以Y=C+I+G+EX-IM這個算式表達,其中Y是GDP,C是消費,I是實質投資,G是政府開支,EX是出口,IM是進口。一般讀者會誤以爲進口IM的前面有减號,便得出IM增加、Y相應减少的結論。但這條公式只是會計結果,即在産量已成定局時(如去年的GDP)要找出它的總值,較簡單的做法就是計算公式右邊各組成部分的總和而已。若要瞭解進口或貿易逆差和GDP的關係,還得要加入有關的經濟行爲假設和分析,不能簡單地從這公式看出來。
進口與投資消費會互相抵消

舉例來說,若美國企業因預期關稅上調而提早從外國入貨,不錯會增加IM,但這不是唯一的經濟活動。如果貨品進口後暫時存入貨倉,那在上述公式中,企業的庫存投資(也就是I的一部分)會和進口同時上升,互相抵消而不會改變Y。如果貨品即時售予消費者,那等于消費增加,公式中的C亦會和進口同時上升及互相抵消。

同樣地,如果貨品是由政府而非企業進口,那麽G也會相應提高。

換句話說,美國本年首季GDP輕微收縮,與美國爭取在關稅提高前增加進口無關,而是其他原因導致。同理,IM數值的改變,一般都有相應的C、I、或G的改變而不影響到本地生産。

如果進口是用來替代本地産品,若消費者减少購買本地産品,轉買外國産品,那本地生産自然下跌。不過,嚴格來說,進口行爲幷不直接减少本地生産,後者下跌只是因消費者爲某些原因先不購買本地産品。若果原因是外國産品價廉物美,本地貨品難以競爭,那减少沒有競爭力行業的本地生産,讓廣大消費者購買更便宜的進口貨,是適當的安排,說不定騰出來的資源可轉移到更有優勢的行業。此外,進口和本地生産不一定互相取代,也可能是互相補充,特別是進口的是零部件或原材料,在這情况下,進口愈多,本地生産也會愈高。

總而言之,進口多少或貿易逆差多大,和本地生産總值的關係有多個可能性,幷非進口愈多本地生産必然愈少。反過來說,以關稅或其他貿易壁壘來限制進口,不一定會帶動本地生産,甚至可能弄巧反拙。過去數年,美國的進口總值持續擴大,但美國的失業率都維持在接近4%的歷史低位(新冠肺炎期間除外),與進口會减少本地生産的說法不符。
逆差與外資流入無因果關係

另一條被特朗普團隊誤用的宏觀經濟恒等式,是經常賬逆差等于淨外資流入。經常賬的主要部分是貿易餘額,爲簡單起見這裏就不考慮其他較小的部分。外資流入就是外國資金爲本地所用,也等于外國貸款給本地。

這兩者之所以恒等,以美國爲例,美國的貿易逆差能够成爲事實,或美國人用外國産品可以多于外國人用美國産品,無論在個人或企業層面如何安排,歸根究柢是美國人多用的外國産品是外國暫時借給美國的。美國的貿易逆差愈大,等于向外國討債愈多、或外資流入愈多,兩者同時出現,是一個硬幣的兩邊。

即使美國發行美元來支付貿易逆差,也等于欠外國債務,因爲美元是美國聯儲局的負債,亦是外國美元持有者的資産,只不過美元現金這個資産的名義回報率是零,低于美元債券而已。

經常賬逆差等于資金流入量這個恒等式,同樣是會計結果,不代表任何因果關係,特朗普團隊却作如下的論述。

由于美元是最主要的外匯儲備貨幣,衆多的外國央行均在外匯市場買入美元,使美元相對其他貨幣升值,導致美國多進口少出口,形成長期龐大的貿易逆差、製造業萎縮、工人失業及依賴外國産品,同時外國則有貿易順差,將從美國賺到的美元轉換爲美國政府債券。當外國持有的美債愈來愈多,會威脅到美元作爲儲備貨幣的地位及美國的國家安全。

換句話說,外國資金流入美國持有美元美債,導致美國外貿逆差及製造業流失,似乎是說美國多年來爲全球提供外匯儲備貨幣,竟要承擔經濟上損失,特朗普爲使美國再次偉大,减少美國的「委屈」,便一方面對衆多貿易夥伴大幅加征關稅,以及萌生將現有美債轉換爲百年無息長債的想法等。

然而,上面的論述與實際情况幷不相符,首先是外國央行持有的美國政府債券,自2012年起至去年底都徘徊于4萬億美元左右,甚至有些下跌【注2】。

這反映總的來說,外國央行在這期間幷沒有加持美國政府債券作爲外匯儲備,惟美國的經常賬逆差仍在2020年後增加很多。

其次,若以製造業雇員占全國非農業雇員的比例來代表製造業占美國經濟重要性的話,這比例從二戰結束時的35%持續有序地下跌至目前的約8%【注3】。但期間美元匯價經歷了多次大幅波動,如在1985年廣場協議後美元的實質有效匯率從118大幅貶值至數年後的90,幷持續數年處于低位,可是沒有改變製造業雇員比例下跌的速度和趨勢。

也許政客的經濟論述只是影響輿論及爲政治服務,但特朗普2.0才開始了4個月,經濟政策的邏輯已顯得左支右絀。在去年總統競選時被選民認爲是特朗普强項的經濟政策,到最近路透的調查中只得37%受訪者認同。看來全球經濟政策不確定性指數在未來數年都會在高位波動。

 

注1:https://www.policyuncertainty.com/
注2:https://fred.stlouisfed.org/series/BOGZ1FL263061130Q
注3:https://fred.stlouisfed.org/graph/?g=cAYh

 

陸炎輝博士
港大經管學院榮譽副教授

 

(本文同時於二零二五年五月二十一日載於《信報》「龍虎山下」專欄)