Good morning Hank, it's Tuesday.

So over at CrashCourse, Adrian Hill has just started hosting a great new series on statistics, and in a recent episode called "Mathematical Thinking," she helped me understand the difference between big numbers.

In general, humans are notoriously bad at big numbers. Like, I don't really understand the difference between a billion and a trillion, because they're both, like, a lot. So how am I to process the fact that, for instance, there are over one hundred trillion microorganisms currently living in or on my body?

Poorly, that's how I'm gonna process it, on every level.

But, right, this is one of the things that makes government budgets, for instance, so notoriously difficult to parse. Like the U.S. spends, by the broadest definition, around fifty billion dollars a year in foreign aid, which is a LOT of money, but it's also just over 1% of the federal budget.

Here's another big number: 4.6 billion dollars. That's how much the Bill & Melinda Gates Foundation donated in 2016. That's a lot of money, but it also isn't. If you gave every American an equal slice of that 4.6 billion dollars, we'd each get about 13 bucks.

So there's a lot that 4.6 billion dollars a year can't buy. For instance, it can't pay for enough teachers to serve all the kids who are getting inadequate instruction worldwide. It can't pay for everyone to have access to primary healthcare. And according to current market rates, 4.6 billion dollars will only buy you 32.3 Phillipe Countinhos.

I'm getting sidetracked by Liverpool, but, right, every year Melinda and Bill Gates release an annual letter, which Hank and I have been following for several years now. And this year, the letter takes the form of answering ten tough questions they get.

They range from "Won't saving kids' lives lead to overpopulation?", which is actually an easy one to answer - no, it won't - to more complicated questions like "Why don't you spend more money in the United States?" and "How has Donald Trump affected your work?" and "Is it fair that you have so much influence?"

It's always worth reading the annual letter; there is a link in the doobly-doo below. But I emerged from it with another difficult question: If 4.6 billion dollars a year isn't enough to solve the world's biggest problems, then are we just, like... completely screwed? (I think that's the technical term.)

I actually got to ask Bill Gates about this on a phone call a couple weeks ago, and the first thing he pointed out to me is that not every dollar spent has equal impact.

Gates: "Say a piece of wealth is a rounding error percentage of the global economy, or global wealth. Why can in some cases - like Green Revoluion - a small amount of money have this big effect?"

Quick definition: The Green Revolution was a huge increase in agricultural yields due to better irrigation techniques, better fertilizers, and better seeds. By the late 1960's, it had helped increase the number of available calories per person by 25% and helped decrease the number of people dying from malnutrition worldwide.

Okay, back to the quote.

Gates: There are two things that allow magnification: one is the invention of a new tool - so a magic seed, a magic vaccine. The second is a system of delivery. Systems of activity - like good primary health care, educating farmers - and then tools. Those are the two things that are so disproportionate." 

And on this, I completely agree. Breakthrough technologies can be absolutely transformational, and investing in better systems can be disproportionately effective because those systems can continue to produce good results over time, even after you stopped funding them.

This is why the Gates Foundation is investing in better toilets and new vaccines, but also in primary healthcare systems.

It's also why, when spent well, the U.S.'s foreign aid budget actually can go a really long way. Like, beginning during the George W. Bush presidency, the U.S. invested a few billion dollars a year to improve access to and availability of AIDS treatment in the developing world. That program had lots of flaws, for one thing it focused way too much on abstinence-only strategies, but nonetheless, a 2009 study found that it saved 1.2 million lives.

You probably don't have a billion dollars, but I believe that how each of use chooses to use our resources shapes the world we end up sharing. And that goes for how we spend our money, but also the resources of our attention and our time.

Here's another big number that at the same time is very small: twenty-six thousand ninety-seven. That's how many days the average human born today will live to see. Let's make them count.

Hank, I'll see you on Friday.