2020年第一季度中國爆發了新型冠狀肺炎疫情，由於湖北和武漢被封鎖，多個省市實施隔離措施，導致中國大部分經濟活動暫時中止。第一季度，中國的實際GDP同比縮水6.8%。很多人關注2020年中國的實際GDP水平，它主要取決於兩方面發展，一是疫情過後經濟的復蘇速度，二是經濟刺激措施是否到位。

在表1中，我們按照6.9這一2019年人民幣兌美元的平均價格，分別用人民幣（第2欄）和美元（第3欄）列出了中國從2015年第一季度以來各季度的GDP水平。此外，在第4欄和第5欄列出了GDP的季度同比和環比實際增長率。我們首先注意到，中國的GDP季度同比實際增長率是逐年下降的。而且，在2019年，由於當時中美貿易戰不斷升溫，中國經濟增長明顯放緩，目前仍受其負面影響。從表1可以看出，中國GDP的季度同比增長率已從2019年第一季度的6.4%逐步下降到2019年第四季度的6.0%。如果中國沒有暴發新冠疫情的話，其2020年第一季度GDP有可能比2019年第一季度的21.81萬億元增加大約6.0%，達到23.12（21.81×1.06）萬億元。這是我們對2020年第一季度GDP的假設估計，實際上，2020年第一季的GDP是20.32萬億元。所以，估計新冠疫情給中國帶來的GDP損失是假設GDP與實際GDP之差，即2.8萬億元人民幣（4050億美元），或者說是2019年中國99.09萬億元GDP總值的2.8%。

不過，今年第一季度中國GDP較去年第四季度出現下滑也並不是反常的。對錶1第5欄的觀察表明，這種情況經常會發生。從2015年到2019年，第一季度的非年化GDP均出現環比下降，降幅平均達16.9%。當然，這一降幅與2020第一季度實際下降26.9%不可同日而語。另外，第一季度GDP佔全年GDP的比重往往不到22%，而第四季度GDP在全年GDP中的比重通常超過28%。這是由於中國通常在1、2月份有春節（農曆新年）假，在這期間，所有農業、製造業、採礦和建築活動都會停止。

圖1同樣是顯示按2019年價格計算的中國2015年第一季度以來的GDP水平。對於2020年第一季度，我們在同一個柱子上標出了GDP實際水平（純色）和假設增長水平（條紋），假設增長部分就是我們所估計的新冠疫情給全國GDP造成的損失，即2.8萬億元。圖1清楚地證實了我們通過表1所觀察到的季度GDP的明顯季節性，特別是第二季度的環比增長速度（綠柱到紅柱）要遠遠高於第二季度的同比增長速度（紅柱到紅柱）。事實上，在過去五年里，第二季度GDP的環比平均增長率達到11.4%（見表1第五欄）。

因此，在正常情況下，2020年第二季度的GDP預計將比第一季度增長11.4%，，達到22.64萬億元（20.32×1.114）。預計第三季度GDP將比第二季度增長4.3%，達到23.61萬億元，第四季度增長10.3%，達到26.04萬億元。就2020年全年來說，把2020年第一季度的實際GDP與第二、第三、第四季度的預測GDP加起來，全年GDP預計為92.61萬億元。比2019年的99.09萬億元低了6.5%，這個數字似乎是太低了。而且，這些預測都是基於這樣的假設，即中國沒有出現復蘇效應，也沒有出台額外的經濟刺激措施。

上述分析的一個主要缺點是，沒有考慮到2020年第二季度的增長只是達到先前已有的產出水平，而不是新一輪增長，所以，它的增長速度實際上應該更快。想想看，一個經濟體由於某種原因收縮了50%，如果它能夠把產出恢復到收縮前的水平，那麼即使只收縮50%，它也是在收縮後的基礎上增長了100%。因此，假設在經濟一旦恢復正常的情況下，2020年第二季度的GDP至少恢復到2019年第四季度的水平，這也不是不合理的。2020年第一季度的GDP比2019年第四季度下降了26.9%，2020年第二季度的GDP要想恢復到2019年第四季度的水平就必須環比增長36.8（26.9/（1-0.269））%。這很高，但並非不可能，因為它只說明收復了失地。如果第二季度GDP為27.80（20.32×1.368）萬億元，第三、第四季度分別預計為29.00（27.80×1.043)萬億元和31.98 （29.00×1.103）萬億元，則2020年全年的GDP預計將達109.1萬億元，比2019年增長10.1%。不過，如果2020年第二季度GDP為27.80萬億元的話，意味着當季的同比增長率達到14.6%，這似乎有點太高了。

另一個可供選擇的假設是，2020年第二季度GDP將恢復到與2019年第二季度的24.26萬億元持平，當季增長率為19.4%，而不是36.8%。由此，預計2020年第三、第四季度GDP分別為25.30（24.26×1.043）萬億元和27.90（25.30×1.103）萬億元。基於這些推測，2020年的GDP預計為97.78萬億元，也就是收縮1.4%。

然而，到目前為止，所有關於內地重開和復蘇的數據都表明，2020年第二季度GDP最可能的結果是同比增長6.0%，也就是說達到25.71（24.26×1.06）萬億元，這意味着環比增長26.5%。相應的，2020年第三、第四季度的GDP預計為26.82（25.71×1.043）萬億元和29.58（26.82×1.103）萬億元。這樣，2020年全年的GDP預計為102.43萬億元，比2019年增長3.4%。不過，所有這些預測仍然是基於沒有額外經濟刺激的假設。

雖然全年增長10.1%可能顯得過於樂觀，收縮1.4%可能顯得過於悲觀，但2020年增長3.4%看來還是相當合理的。然而，所有預測都是基於沒有新的經濟刺激這樣一種假設。如果有額外經濟刺激，則內地經濟當能在2020年的第三、第四季度以更高速度增長。如果我們假設有刺激經濟的措施，2020年第三、第四季度的環比增速會比正常的增長速度高出25%，季度GDP將分別達到27.09（25.71×1.054）萬億元和30.58（27.09×1.129）萬億元。按照同比計算，2020年四個季度的實際與預期經注增長速度分別為-6.8%、6.0%、7.4%和10.0%。

如果把2020年各個季度的實際和預計GDP加起來，則2020年全年的實際GDP預計是103.70萬億元，比2019年增長4.65%，這是在有額外經濟刺激的情況下。然而，正如上面所提到的，如果沒有任何經濟刺激的話，2020年的GDP增長速度有可能是3.4%左右。與此同時，如果全球其他經濟體在第三、第四季度也出現復蘇，那麼中國的經濟增長會更快，全年有可能超過5%，這也是在有額外經濟刺激的情況下。當然了，在2020年剩下的時間裡，中國內地經濟復蘇的速度究竟有多快，仍有待觀察。我們的假設和預期是，在2020年剩下的三個季度里，中國經濟的增長速度會大大高於正常水平。

In 2020Q1, there was an outbreak of the COVID-19 epidemic in China, which resulted in the temporary cessation of most economic activities in China due to the blockade of Hubei and Wuhan and lockdowns in many provinces and cities. Chinese real GDP declined by 6.8 percent, year-over-year, in the first quarter of 2020. A great deal of interest is focussed on the level of Chinese real GDP in 2020. The Chinese GDP in 2020 depends crucially on two developments—the speed of the economic recovery from the COVID-19 epidemic and the availability of additional economic stimulus.

In Table 1, the levels of Chinese quarterly GDP in 2019 prices since 2015Q1 are presented in both Yuan (column 2) and US$ (column 3) at the average Yuan/US$ exchange rate over 2019 of 6.9 Yuan per US$. In addition, the quarterly year-over-year as well as the quarter-over-quarter real rates of growth are also presented in columns 4 and 5 respectively. We note, first of all, that the Chinese quarterly year-over-year real rates of growth have been declining gradually over the years. Moreover, in 2019, Chinese economic growth slowed down significantly because of the then rising China-U.S. trade war, and continues to be adversely affected by it. Table 1 shows that the quarterly year-over-year rate of growth declined gradually from 6.4% in 2019Q1 to 6.0% in 2019Q4. If there were no COVID-19 epidemic in China, the 2020Q1 GDP would probably have been approximately 6.0% higher than the 2019Q1 GDP of 21.81 trillion Yuan, or 23.12 (21.81 x 1.06) trillion Yuan. This would be our estimate of the hypothetical 2020Q1 GDP. The actual 2020Q1 GDP was 20.32 trillion Yuan. Thus, the loss of Chinese GDP due to the COVID-19 epidemic may be estimated as the difference between the hypothetical and the actual GDP, that is, 2.8 trillion Yuan (US$405 billion), or 2.8 percent of the 2019 Chinese national GDP of 99.09 trillion Yuan.

However, a decline in Chinese GDP in the first quarter from the fourth quarter of the previous year is not unusual. An inspection of column 5 of Table 1 suggests that it occurs regularly, with an average non-annualised quarter-over-quarter decline of 16.9% between 2015 and 2019, but of course, not quite of the same magnitude as the decline of 26.9% actually realised in 2020Q1. Moreover, the first-quarter GDP typically accounts for less than 22 percent of the annual GDP, whereas the fourth-quarter GDP typically accounts for more than 28 percent of the annual GDP. This is due to the Spring Festival (lunar new year) holiday in China, which typically takes place between January and February, with all agricultural, manufacturing, mining and construction activities ceased.

The levels of Chinese quarterly GDP in 2019 prices since 2015Q1 are also presented in Chart 1. For 2020Q1, we show in the same column both the actual level (in solid colour) and the hypothetical increase (in striped colour) of real GDP, with the hypothetical increase being our estimate of the loss in national GDP attributable to the COVID-19 epidemic, 2.8 trillion Yuan. Chart 1 clearly confirms the pronounced seasonality in the quarterly GDPs observed in Table 1. In particular, the rate of growth between Q1 and Q2 (from green column to red column) is much higher than the year-over-year growth rate of Q2 GDP (from red column to red column). In fact, the average rate of growth of GDP between Q1 and Q2 is 11.4% over the past five years (see Table 1, column 5).

Thus, normally, 2020Q2 GDP is expected to increase by 11.4%[1] from 2020Q1, so that the 2020Q2 GDP may be projected to be 22.64 (20.32 x 1.114) trillion Yuan. The 2020Q3 GDP is expected to increase by 4.3%[2] from 2020Q2, to 23.61 trillion Yuan. The 2020Q4 GDP is expected to increase 10.3%[3] to reach 26.04 trillion Yuan. For 2020 as a whole, by adding the actual 2020Q1 and the projected 2020Q2, Q3 and Q4 GDPs together, we obtain a projected annual GDP of 92.61 trillion Yuan. This represents a decline of 6.5% from the 2019 GDP of 99.09 trillion Yuan, which seems excessively low. Moreover, these projections are all based on the assumptions that there is no recovery effect and there will be no additional economic stimulus in China.

A major weakness in the above analysis is its failure to take into account that in 2020Q2, it is a recovery to a previously achieved level of output and not a fresh round of new growth, and hence should be more rapid. Consider an economy which has contracted by 50%, for whatever reason, if it is able to restore its output to just before the contraction, it will have grown 100% from the shrunken base, even though the contraction was only 50%. It is therefore not unreasonable to assume that GDP will be restored to at least the level of 2019Q4 in 2020Q2, once things return to normal. 2020Q1 GDP declined by 26.9% from 2019Q4. In order for 2020Q2 GDP to recover to the 2019Q4 level, it will have to grow at 36.8 (26.9/(1-0.269)) % quarter-over-quarter in 2020Q2[4]. This is high, but not impossible, because it just represents recovery of lost grounds. With a 2020Q2 GDP of 27.80 (20.32 x 1.368) trillion Yuan, the 2020Q3 and Q4 GDPs may be projected successively as 29.00 (27.80 x 1.043) and 31.98 (29.00 x 1.103) trillion Yuan. This results in a projected GDP for the whole of 2020 of 109.1 trillion Yuan, or a rate of growth of 10.1% over 2019. However, a level of 2020Q2 GDP of 27.80 trillion Yuan implies a year-over-year rate of growth of the 2020Q2 GDP of 14.6%, which seems a little too high.

Still another possible alternative assumption is that the 2020Q2 GDP will recover to the same level as the 2019Q2 GDP of 24.26 trillion Yuan, a quarterly rate of growth of 19.4% instead of 36.8%. The 2020Q3 and Q4 GDPs can therefore be projected to reach 25.30 (24.26 x 1.043) and 27.90 (25.30 x 1.103) trillion Yuan respectively. These projections result in a projection of 2020 annual GDP of 97.78 trillion Yuan, implying a contraction of 1.4%.

Yet all the data on the re-opening and recovery on the Mainland to date suggest that the mostly likely outcome of 2020Q2 GDP is a year-over-year growth of 6.0%, that is, it would reach the level of 25.71 (24.26 x 1.06) trillion Yuan, implying a quarter-over-quarter rate of growth of 26.5%. The corresponding 2020Q3 and Q4 GDP's may be projected successively as 26.82 (25.71 x 1.043) and 29.58 (26.82 x 1.103) trillion Yuan. This results in a projected GDP for the whole of 2020 of 102.43 trillion Yuan, or a rate of growth of 3.4% over 2019. However, all of these projections are still based on the assumption of no additional economic stimulus.

While a 10.1% annual rate of growth may appear too optimistic and a 1.4% contraction may appear too pessimistic[5], a 3.4% annual rate of growth for 2020 seems quite reasonable. However, all of these projections are predicated on the assumption of no new economic stimulus. If there were additional economic stimulus, the Mainland economy should be able to grow at higher rates in 2020Q3 and Q4. If we assume that with additional economic stimulus, the Mainland economy can grow at a rate 25% higher than the normal quarter-over-quarter rates of growth in 2020Q3 and Q4 respectively, it results in projections of 2020 quarterly GDPs of 27.09 (25.71 x 1.054) trillion Yuan and 30.58 (27.09 x 1.129) trillion Yuan respectively. On a year-over-year basis, the actual and our projected rates of growth of the four quarters in 2020 are -6.8%, 6.0%, 7.4% and 10.0% respectively.

If we now sum up the actual and these projected levels of quarterly GDPs for 2020, we obtain a projection of 2020 real GDP of 103.70 trillion Yuan, or an increase of 4.65% from 2019, with additional economic stimulus. However, without any economic stimulus, the rate of growth of GDP for 2020 is likely to be around 3.4%, as we have seen above. If, in the meantime, the rest of the global economy also recovers in 2020Q3 and 2020Q4, the Chinese rates of growth would be even higher, perhaps even exceeding 5% for 2020 as a whole, with additional economic stimulus. Of course, it remains to be seen how fast the Mainland economy will be able to recover for the rest of 2020. Our assumption and expectation is that the rates of growth for the remaining three quarters of 2020 will be significantly above normal.