Scientists have made a breakthrough! They've discovered a subplane of our reality that consists of what can only be described of as the essence of luck. There's also a reasonably easy way to tap into this plane and use this essence! You can also decide how much luck you want to use with a reasonable degree of precision.
Using this essence makes you lucky — if you were to use enough of it while buying a lottery ticket, for example, you'd certainly hit the jackpot!
However, there is a catch. Luck essence, like matter and energy, is conserved. Unlike matter and energy it doesn't need to be conserved at a specific point in time, so you can draw good luck now and pay it back later. It's best to pay it in advance, though — a luck surplus is quite stable regardless of how large your surplus is and will be available whenever you need it, but luck debt is more and more unstable the larger it is and has a tendency to unexpectedly pay itself back.
This luck also can't be transferred. There's no way to have someone else give you their good luck, or take your bad luck.
Of course, you're probably wondering what happens when you use luck at the same time as someone else. The simplest way to describe it is that using luck makes your situation better than it would have been, while storing or paying back luck makes your situation worse than it would have been. Using the lottery example again, you'll still hit the jackpot when you otherwise would not have, but with 1000 other people doing the same thing your winnings are going to much less. Unfortunately even though your result isn't as good as it would have been had others not used their luck, you use just as much luck either way.
It's possible to have your good luck help someone else too, and it won't even give them a luck debt. This means you can safely use luck as you attempt to cook the best Thanksgiving dinner ever. On the other hand, your bad luck also can't give anyone a luck surplus, so foolishly choosing to pay back luck while driving a car won't be of any benefit to the other people involved in the subsequent wreck.
Also, you can't control exactly what effect the (good or bad) luck will have other than by context of where you are and what you're doing at the time, but your luck will have some effect. Trying to pay back luck while buying a lottery ticket is rather risky because there's a good chance that you wouldn't have won anything anyway, so the payback will likely take another form (like someone accidentally kicking you in the groin on your way out).
A PLAN FOR LUCK:
When they announce their discovery, the scientists also propose a plan (and secretly use some luck to make sure it is well-received). Economies and innovations are not a zero-sum game — if I give you something you value (such as money) for something that I value (food), then we are both better off than before. Innovation is particularly good at this — many of the world's problems could be solved with the help of a discovery of working cold fusion or some other cheap, clean, and efficient energy source.
As such, it is in the interest of governments around the world to try to make as much good luck as possible available to as many people as they can. This would maximize the chance of someone stumbling across the next world-changing invention.
However, the scientists don't know what the best way to give everyone luck is. One way would be to have a cheap lottery with a good chance of winning at least a small amount. You'd be able to afford to buy a large number of tickets, meaning that you'd be all but guaranteed to have some winning tickets if you were not storing up luck. However, with the tickets being cheap and the prizes not being great (otherwise people would just decide they don't need to use luck essence in order to be lucky), you'll only be able to store up a little luck at a time.
So given the resources of Earth's current governments, what would be the best way to help as many people store up as much luck as possible without incurring significant risk as they do so?
Note: When you store luck something will go worse than it would have, with how much worse being proportional to how much luck you're storing. So in order to be effective, in whatever system the government sets up there has to be some way for storing luck to make your personal outcome worse, otherwise you're going to have some other kind of misfortune come your way (for example, if you stored quite a bit more luck than the system could accommodate you could get a heart attack and die).
Also, you have to decide ahead of time how much luck you'll store — in a normal lottery if everyone who played decided to store enough luck to not get the jackpot, any person who would have won the jackpot will simply not win anything, but the people who would not have won the jackpot anyway are in for a bad time (i.e likely gonna die).
