Bill Gates has given his answer for the best investment he's ever made

With a net worth of more than a billion dollars, Bill Gates is no stranger to investing his money. And after decades of experience the business magnate has revealed what he believes to be his best investment.

Gates made his fortune by co-founding Microsoft in 1975, but over the years has started a charitable foundation and invested in a number of causes, including zero-carbon energy and the health sector.

According to The Investors Podcast, Gates currently still has investments in businesses such as the construction machinery and equipment company Caterpillar, the Canadian National Railway Co. and Walmart, but it's not those that he's deemed to be the best places he's spent his money.

In a clip shared by The Investor, the businessman could be heard talking about the best investment he'd ever made after he wrote an article on the subject in The Wall Street Journal in 2019.

Gates explained that this particular investment was one made through his foundation over the course of 20 years, during which time more than $10 billion was invested into a number of organisations.

The companies were 'health delivery organisations', in particular one which 'buys vaccines for the poorest countries', named Gavi, and one which 'buy drugs for HIV and Malaria'.

Gates explained that these companies have had 'quite a dramatic impact', so he stressed that 'any way you look at it', the investments were a solid choice from a 'humanitarian point of view' or an 'economic point of view'.

They were 'clearly one of the best investments I've ever been involved in', Gates said.

In his article for The Wall Street Journal, Gates explained that while developing new medicines and vaccines is key to saving lives, so is the journey of those treatments to where they need to be.

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"Over the past two decades, my wife Melinda and I have put a total of $10 billion into organizations that do this challenging work, including three big ones: Gavi, the Vaccine Alliance; the Global Fund; and the Global Polio Eradication Initiative. Each of them has been extremely successful, but most people don’t know their names or what they do," Gates explained at the time.

After Gavi was founded in 2000, Gates said the number of children under the age of five dying in low- and middle-income countries dropped by about 40 percent.

Though he anticipates 90 percent of his technology investments to fail, the few that succeed have, evidently, done so 'wildly'.