????美國(guó)國(guó)會(huì)預(yù)算辦公室（Congressional Budget Office）最近公布了新的預(yù)算估算報(bào)告。這份報(bào)告已經(jīng)讓評(píng)論人士迎來(lái)了一系列感覺(jué)良好的時(shí)刻。他們表示，債務(wù)已經(jīng)得到控制。他們指出，聯(lián)邦醫(yī)療保險(xiǎn)（Medicare）的預(yù)期成本將繼續(xù)下降。他們還宣稱，根據(jù)國(guó)會(huì)預(yù)算辦公室的估算，未來(lái)的利率水平也將下降，利息支出因而將減少。在一片歡呼雀躍聲中，值得指出的是，有兩個(gè)事實(shí)可能會(huì)延緩他們宣布贏得這場(chǎng)赤字戰(zhàn)爭(zhēng)“勝利”的時(shí)間。

????首先，和歷史正常水平相比，美國(guó)政府的債務(wù)總額仍處于高位。目前，聯(lián)邦政府債務(wù)占美國(guó)GDP的74%，除了二戰(zhàn)前后的7年，這是該比率有史以來(lái)的最高水平。二戰(zhàn)結(jié)束時(shí)，美國(guó)的政府債務(wù)占GDP的比率為106%，但隨后快速下降，原因是低利率、低通脹以及維持了二三十年的強(qiáng)勁經(jīng)濟(jì)增長(zhǎng)。如今我們只能盼望著這樣的經(jīng)濟(jì)發(fā)展勢(shì)頭能在短時(shí)間內(nèi)再次出現(xiàn)。

????但是，政府債務(wù)占GDP比率預(yù)期不會(huì)下降。今后十年內(nèi)，這個(gè)數(shù)字預(yù)計(jì)將緩慢上升，隨后還將迅速增長(zhǎng)。以前，人們擔(dān)心政府債務(wù)將達(dá)到很高的水平，比方占GDP的74%。而現(xiàn)在，這已經(jīng)成為現(xiàn)實(shí)。在“經(jīng)濟(jì)大衰退(Great Recession)”之前，就算布什政府大幅度減稅，增加社會(huì)福利，提高國(guó)內(nèi)支出并擴(kuò)大軍事行動(dòng)規(guī)模，那時(shí)的政府債務(wù)占GDP比率也只有現(xiàn)在的一半。

????有意思的是，在當(dāng)時(shí)的情況下，許多人都認(rèn)為美國(guó)負(fù)擔(dān)不了喬治?W?布什總統(tǒng)的開(kāi)支計(jì)劃。如今，在政府債務(wù)占GDP比率達(dá)到74%，并且預(yù)期還將進(jìn)一步增長(zhǎng)之際，這些人卻覺(jué)得沒(méi)什么可擔(dān)心的。

????然而，就像國(guó)會(huì)預(yù)算辦公室所提醒的那樣，赤字增多會(huì)擠占投資空間，降低經(jīng)濟(jì)增長(zhǎng)率，降低美國(guó)民眾生活水平的提升速度。更廣義地講，如果居高不下的政府債務(wù)占GDP比率不產(chǎn)生任何政治和經(jīng)濟(jì)成本，許許多多國(guó)家就會(huì)在“經(jīng)濟(jì)大衰退”之前出現(xiàn)高額凈負(fù)債。畢竟，如果政府債務(wù)占GDP比率無(wú)關(guān)痛癢，許多國(guó)家就可以毫無(wú)顧忌地增加開(kāi)支并減稅。而實(shí)際上，政府債務(wù)占GDP比率超過(guò)70%的國(guó)家少之又少。無(wú)論是以往，還是和別的國(guó)家相比，如此高的政府債務(wù)都不是好現(xiàn)象。

????其次，目前預(yù)測(cè)的赤字水平可能會(huì)讓人們無(wú)端地產(chǎn)生自滿情緒，原因是這樣的預(yù)期既暗含了經(jīng)濟(jì)好轉(zhuǎn)，還體現(xiàn)了政府支出和收入趨勢(shì)的改善。從下圖可以看出，在國(guó)會(huì)預(yù)算辦公室預(yù)測(cè)的基準(zhǔn)情景中，今后5年內(nèi)，政府赤字占GDP的比率基本上都將保持在3%以下，隨后略有上升。

????The Congressional Budget Office recently put out new budget projections and commentators have had a series of feel-good moments about it. Debt is under control, they say. Projections of Medicare costs continue to fall, they point out. The CBO’s estimates of future interest rates, and hence interest payments, have come down as well, they echo. Amidst all of the congratulations, it is worth pointing out two facts that might give one pause in claiming “victory” in the deficit wars.

????First, the overall debt level is already high relative to historical norms. At its current level of 74%, the ratio of federal debt-to-GDP is at its highest ever, except for seven years around World War II. At that time, the debt ratio peaked at 106% at the end of the war and then fell rapidly, due to low interest rates, inflation, and a generation’s worth of strong economic growth that we can only hope to see again anytime soon.

????Now, however, the debt-to-GDP ratio is not projected to fall. It is projected to creep up slowly over the next decade and then more rapidly in the future. It used to be the case that people worried about whether the debt would increase to high levels – like 74% of GDP. Now, we have arrived there. Before the Great Recession, even with the major tax cuts, new entitlements, increased domestic spending and the expanded military operations of the Bush administration, the debt-to-GDP ratio was just half as big as it is now.

????It is interesting that many people who thought former U.S. president George W. Bush’s agenda was unaffordable back when the debt-to-GDP ratio was half as big as it is now feel that a ratio of 74% is nothing to worry about as debt is predicted to rise further.

????But higher deficits, as the CBO reminds us, will crowd out investment, reduce economic growth and reduce the increase in living standards for the population as a whole. More generally, if sustaining a high debt-to-GDP ratio were politically and economically costless, one would have seen many more countries, before the Great Recession, in high net debt territory. After all, countries could spend more and cut taxes with impunity if the debt-to-GDP ratio didn’t matter. In fact, very few were above 70 percent. It is not a good place to be historically nor comparatively.

????Second, the current projections of the deficit could prompt unwarranted complacency because they reflect both an improving economy and underlying spending and revenue trends. The figure below shows the CBO’s baseline projection that deficits are basically flat at just under 3% of GDP over the next five years, then rise slightly.