全球人口估計在10月31日將超過70億，許多政策制定者的短期憂慮，都圍繞在如何提供資源給未來50年所出生的20到30億人。

With the global population estimated to pass 7 billion on Oct. 31, many of policymakers' short-term worries revolve around providing resources for the additional 2-3 billion people expected to be born in the next half-century.

這個天文數字讓人很難不去聯想到匱乏與混亂的恐怖局面。但事實上，糧食生產及科技的進步，已允許人口能持續且相對平穩地增長。真正潛在的隱憂，反而是人口快速老化，以及窮國及富國都面臨到的出生率遽降。

Numbers of this magnitude inevitably conjure up terrifying visions of shortage and chaos. But in fact improvements in food production and technology have allowed population growth to continue unimpeded and relatively smoothly, and the real potential nightmare is of a rapidly ageing （1）population, combined with collapsing birthrates （2）in both rich and poor states.

許多人口學家及長期政策規劃者表示，未來一世紀的挑戰主要是來自於更多的老化人口，而不是人口增加。

Many demographers and long-term planners say the challenge for the next century will be less dealing with growing numbers of people and more managing the much larger population of aged.

此一趨勢已影響到目前的全球財務危機，各國的醫療及社會福利支出都在增加，生產力可能也因此折損。當政客的視野僅侷限在短期憂慮時，專家們認為長期的人口結構挑戰沒有獲得充分獲得討論。

The trend has already contributed to the current global financial crisis by driving up health and social care bills and perhaps also undermining productivity. But while politicians tie themselves in knots over short-term worries, experts say there is not enough discussion of longer-term demographic challenges.

哥德斯通是華盛頓喬治梅森大學的公共政策教授，同時也是一名人口學專家，他說：「我們認為人口過多迫使人類朝外太空的其它星球發展，但這看起來完全不是問題。解決這些長期問題的政策框架完全還未設立。」

"We thought that overpopulation （3）was going to force humanity to expand outward to the stars. That doesn't look like the problem at all. And the policy framework isn't set up at all to handle these longer-term issues," says Jack Goldstone, professor of public policy and a leading demographics （4）expert at Washington's George Mason University.

許多貧困國家的人口持續在強勁成長，全球生育率（每對夫妻所生的孩童數）仍保持在2.5左右，足可替代現存的每一個人。

With many of the world's poorer countries still seeing strong growth, the global fertility （5）rate -- the number of children born per couple -- remains around 2.5, more than enough to replace every person currently alive.

但較為富有的國家，生育率大幅下降。俄羅斯、新加坡及許多其他已發展國家都引進辦法來刺激生育，儘管成敗參半。

But in richer countries, the rate has already nosedived. Russia, Singapore and several other developed countries have introduced policies to boost fertility but with mixed success.

確切的預估仍在變動，但大多數的預測都指出，全球人口約在2070年將來到90億左右的巔峰，隨後可能會以極快的速度下降。

Exact predictions vary, but most projections suggest the global population will peak at around 9 billion around 2070 and then start to fall, perhaps very fast.

在世界銀行鑽研拉丁美洲的人口專家寇特李爾表示：「生育率下降在已發展世界已是確切趨勢，但大多數中等收入國家也正在快速下降，甚至連某些成功的低收入國家也是如此。」

"The decline in fertility has gone the furthest certainly in the developed world but it is falling very rapidly in most middle-income countries and even some of the more successful lower-income countries," said Daniel Cotlear, a population expert at the World Bank specialising in Latin America.

等到2030年，某些西方國家及諸如日本及韓國等亞洲經濟體，將有超過1／3的人口會老於65歲。許多開發中國家也加入這股潮流，尤其是執行一胎化政策的中國，但這些國家往往沒有支付醫療及照護支出的財政資源。

By 2030, more than a third of the population in a number of Western states as well as some Asian economies, such as Japan and Korea, will be aged over 65. Many developing states, most notably China with its one-child policy, will follow suit -- often without the financial resources to help pay for the cost of medical and nursing care.

總部設在紐約的全球老齡聯盟執行主任霍丁表示：「這是我們這個時代的重要議題。數字是驚人的，準確的估算還在變動，但這不打緊，因為他們全都往同一個方向邁進。」霍丁同時也是外交關係協會的高級研究員。

"It's the seminal issue of our time," says Michael Hodin, executive director of the New York-based Global Coalition on Ageing and a senior fellow at the Council on Foreign Relations. "The numbers are stunning. The exact projections vary but it doesn't really matter because they are all going in the same direction."

在已發展世界，大多數國家依賴人數眾多的勞動賦稅人口，由他們來支付年長者的照護支出及退休金，而老年人的數量相對較少。在比較貧窮的國家，則有大家庭在負責照顧年長者。但專家表示，這些模式都無法因應老人變多、年輕人變少的人口結構。

In the developed world, most countries rely on a large number of working taxpayers to pay for the care and pensions of a relatively small group of elderly people. In poorer countries, extended families tend to look after the elderly. Neither of those models, experts say, is designed to cope with the changed demographics of more old and fewer young.

短期來說，許多富裕國家會透過從世界其它地方引進年輕人來彌補人口結構的缺口。但這也不是長遠之計，因為勞動力的來源遲早會因生育率的下降而枯竭。

In the short-term, many rich countries have plugged the demographic gap by importing young people from elsewhere in the world. That, too, may become unsustainable in the years to come as those sources of labour dry up due to falling fertility rates.

維也納人口統計學研究所的研究團隊領導者薛波弗說：「這將會是個更老的社會，但這也將是個教育程度更高的世界。民眾變得更健康，我個人認為我們應該根據這些態勢做出調整。」

"This will be a much older world but it will also be a much more educated world," said Sergei Scherbov, research group leader at the Vienna Institute of Demography. "People are becoming healthier. I personally think we will adjust to these things."

最大的問題在於目前沒人能清楚回答，是否有可能在擘劃經濟成長的同時，讓老年工作者及成為勞動力的年輕人都擁有工作及希望。

The biggest question that no one has any clear answer to at present, experts say, is whether it is possible to plan for economic growth that will provide jobs and hope for both older workers and those younger people entering the workforce.

在世代衝突這一最壞情況下，老年人與中年人會霸占工作機會，並積極展開遊說來維持無以支撐下去的權利；而年輕人感覺自己的機會被剝奪，並被迫由他們來償付這些財政支出。有部分人士認為，在某些已發展國家已經可以觀察到這個現象的出現。

In a worst-case scenario of generational conflict, an elderly and middle-aged cohort might block jobs and lobby ferociously to keep up unsustainable entitlements while an angry youth feel denied opportunities and are forced to pay the ultimate financial bill. Some believe that phenomenon is perhaps already becoming visible in parts of the developed world.

哥德斯通表示：「人口老化的真正問題是經濟成長問題。如果我們有成長，我們就可負擔老一輩的養老金及醫療保健；但如果我們沒辦法，所有人都要一同受罪。」

"The real problem about the ageing population is an economic growth problem," says George Mason University's Goldstone. "If we have growth, we can afford the pensions and healthcare for the older generation. But if we don't, everyone is going to suffer."

（路透Reuters）

1. ageing

(a.) 老化的、變老的

2. birthrate

(n.) 出生率

3. overpopulation

(n.) 人口過剩

4. demographics

(n.) 人口特質、人口（年齡、收入等）結構

5. fertility

(n.) 生育、繁殖

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