In Luanda?s Jumbo supermarket, a half-litre tub of imported vanilla ice-cream used to cost $25 (£15), testament to the Angolan capital?s rank as one of the world?s most expensive cities. With new import tariffs imposed last month, that price has jumped to $31, enough to make even wealthy locals and expatriates pause and putting the treat even further beyond the reach of millions of poor Angolans struggling to feed their families. Luanda already ranks as the world?s most expensive city for expatriates, with the presence of thousands of foreign workers, many involved in the oil industry, helping to drive up prices. Sub-Saharan Africa?s second-largest oil producer, still rebuilding after it...