Here is Bill Gates:

Usually, “optimism” and “realism” are used to describe two different outlooks on life. But I believe that a realistic appraisal of the human condition compels an optimistic worldview. I am particularly optimistic about the potential for technological innovation to improve the lives of the poorest people in the world. That is why I do the work that I do.

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Consider the example of M-Pesa, Kenya’s mobile-banking service that allows people to send money via their cellphones. M-Pesa first needed to invest in many brick-and-mortar stores where subscribers could convert the cash they earn into digital money (and back into cash). This real-world infrastructure will be necessary until economies become completely cashless, which will take decades.

Without omnipresent cash points, M-Pesa would be no more convenient than traditional ways of moving money around. At the same time, it was impossible to persuade retail stores to sign on as cash points unless there were enough M-Pesa subscribers to make it profitable for them.

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There have been many successful small-scale pilot programmes using cellphones. But examples of large-scale, self-sustaining programmes powered by digital technology, like M-Pesa, are harder to find, because the key pieces have not been put into place to enable the required work to advance beyond the limits of controlled experiments.