What worries Bill Gates most？ Thebooming population of Africa looms over his foundations latest global survey. By the end of this century there will be 4 billion more people on Earth-and 3 billion of these extra souls will be born in Africa. The challenge， he says， is that“Africa must almost quadruple its agricultural productivity to feed itself. Thats very daunting.

The philanthropist is torn between sending out a message of hope and a message of fear when I meet him at his foundations spacious campus in the heart of his hometown， Seattle.

He is reaching for what works best torevive the Wests faltering conscience in theface of“America first”nationalism and rising pull-up-the-draw bridge populismin Europe. The spirit of generosity is under assault as government aid budgets come under constant sniper fire from right-wing politicians and their media.

Half of the Bill & Melinda Gates Foundation spending goes to Africa. The funds put into the foundation by themselves and fellow philanthropist Warren Buffett now amount to more than than $50bn. Until last year Gates， the Microsoft founder， was the worlds richest man. He has now been over taken by Amazons Jeff Bezos.

The foundations report bursts with remarkable data-too few people know aboutthe galloping progress of human kind. Take India， where only 18 years ago almost one in five children were not enrolled in primary school-now， 97% attend classes. Look at the indicatorson the reports global score card for the UNssustainable development goals for 2030， and most things are improving almost everywhere. But there is a marked variation in the future trajectory： progress depends on the level of future investment.

Today， the West takes some persuading that things are getting better， especially in Europe where countries like Britain have suffered a decade of falling real living standards and eye-watering austerity. The upbeat message of Gates-as well as those in his late friend Hans Roslings book Factfulness， and Steven Pinkers Enlightenment Now-telling us most of the world is on an unprecedented up swing， jars with our reality. Yet it is so： the world has never seen such a rapid rise in prosperity among most of the poor.

Eager to encourage Western countries to keep giving aid， Gates is well aware that Britain-as else where-suffers frequent politicalattacks on its aid budget. The UK， Sweden and Norway are among the few reaching the UNaid spending target of 0.7% of gross nationalin come， and all feel the cold blast of an anti-foreigner political grudge. “If you are saving lives for a very small amount of money， people should feel good about that，” Gates says emphatically， protesting at current cynicism about internationa laid organisations. Look what can be done， he keeps saying， pointing as an example to the brilliant education system in Vietnam， a poor country whose results outstrip far richer ones.

If Britain needs encouragement， he says， “the data about the impact has been amazing. The UK has been very generous to the vaccine fund， for two vaccins—one for pneumonia， one for diarrhoea.” These sicknesses are now preventable“at extremely low cost to all the children of the world. The UK led that effort and saved over 10 million lives”. Do people across the UK know that？ He admits a failure to spread the good news. “We re being challenged to explain.” Everyone should know this message of hope. “Were talking about up lifting the human condition in a fairly dramatic way.”

But if hope doesnt beat the new nativism infecting the Western world， then fear is Gates ammunition of last resort. lgnore Africa at your peril. “The stability of Africa makes a huge difference to the entire world.” Here come the threats：“A pandemic like Ebola can spread very fast，” he warns， and many others spread even faster if there are no local health services to contain them.

Migration is the other threat to touch Europes politics. Syria was a small country， he reminds us， yet its civil war exodus has“challenged the asylum system”. But watch out because“Africa is another order of magnitude.The huge African youth boom is a strong the mein the report， where in a world of ageing and shrinking populations， Africas demographicbulge could be an asset or a threat. So it would be wise“to make their lives attractive”not just out of“pure human caring”. Invest in Africas young， their human capital， health andeducation， support more productive agriculture， protect subsistence farmers against climate change and see how self-interest blends with good works.

Africa， he always stresses， is not one country. Of its 54 nations， many are leaping ahead， Ghana， Bot swana and Rwanda among them. Those causing concern are the Democratic Republic of the Congo and Nigeria.

On his recent visit he warned Nigerians against the countrys growing inequality， where oil wealth for a few is leaving millions behind. The found ation has spent $1bn so far on Nigeria. He says，“Their health system is worse than poorer countries， their agricultural advice largely broken down.” Government resourcesare low because“their level of taxation is one of the lowest in the world”.

比爾·盖茨最担心的是什么？在他的基金会最新的全球调查中，非洲人口的迅速增长成为一个隐忧。到本世纪末，地球上的人口将增加40亿，其中30亿人将在非洲出生。他表示，挑战在于“非洲必须将农业产能提高近四倍，才能养活自己。这是非常艰巨的。”

当我在他的基金会，位于他家乡西雅图中心地带的宽敞校园里见到这位慈善家时，他既表达了希望，又表达了恐惧。

面对“美国优先”的民族主义和欧洲日益高涨的民粹主义，他正在寻找最有效的方法，以重振西方摇摇欲坠的良知。由于政府援助预算不断受到右翼政客和其媒体的冷嘲热讽，慷慨的精神受到了攻击。

比尔及梅林达·盖茨基金会一半的开支都花在了非洲。这个基金会现有资金已经超过500亿美元了，主要来自盖茨夫妇和同伴慈善家沃伦·巴菲特。直到去年，微软创始人盖茨还是世界首富。如今，他已被亚马逊的杰夫·贝索斯超越。

该基金会的报告充满惊人的数据——很少有人知道人类的飞速进步。以印度为例，仅在18年前，该国近五分之一的孩子没有小学上，而现在97%的孩子上了小学。看看报告中联合国2030年可持续发展目标的全球记分卡上的指标，几乎所有地方的情况都在改善。但未来的轨迹有一个明显的变化：进展取决于未来的投资水平。

如今，西方国家需要说服一些人相信情况正在好转，尤其在欧洲像英国这样的国家，10年来实际生活水平不断下降和紧缩令人难以忍受。盖茨的乐观信息一以及他已故的朋友汉斯·罗斯林的《事实》——书和史蒂芬·平克的《当下的启蒙》——告诉我们，世界上大部分地区正处于前所未有的繁荣时期，与我们的现实不符。……