GENEVA, Sept. 29. The United Nations estimates that illegal outflows of capital from Africa totaled over $830 billion in the first 15 years of this century, much of it linked to movements of high-value commodities like gold, diamonds, and platinum — straining the ability of the continent’s governments to provide services like healthcare, education, and infrastructure.

The U.N. Conference on Trade and Development on Monday focused the latest edition of its annual report on economic development in Africa to the issue of illicit financial flows, or illegal movements of money and assets across borders. In Africa, it has often involved theft, corruption, and flawed invoicing of shipments.

From 2013 to 2015 — the last year for which data was available — such outflows rose to nearly $89 billion a year on average. By comparison, the combined total of both official development assistance and foreign direct investment received by Africa during that three-year span averaged $102 billion annually.

“Illicit financial flows rob Africa and its people of their prospects, undermining transparency and accountability and eroding trust in African institutions,” said UNCTAD Secretary-General Mukhisa Kituyi. The agency said that total illicit capital flight from Africa amounted to $836 billion between 2000 and 2015.

The largest component of illicit capital flights from Africa, totaling $40 billion in 2015, was related to “extractive commodities” — more than three-fourths of it in gold alone, followed by diamonds and platinum, UNCTAD said. It cautioned the data was incomplete and such figures were likely an underestimate of the true tally.

Illegal capital outflows from three countries — Nigeria, Egypt and South Africa — accounted for more than four-fifths of the total annually during that three-year span, with Nigeria alone making up nearly half of that, according to UNCTAD calculations.

Cracking down on such illegal outflows could help African countries retain capital for investment in roads, railways, schools, and healthcare, the agency said.

UNCTAD said African countries generally aren’t doing enough to reform the international tax system in ways that could help, and said local judicial authorities often lack proper tools to combat tax evasion. (AP)