ELI5: Explain Like I'm 5


Additionality is a big and tricky word that people use when they want to know if something is making a difference.

Let's say you're trying to raise money to buy a new bike. To get the money, you might ask your parents, your grandparents, your aunts and uncles, and your friends. But what if you asked your parents and they said no? Then you asked your grandparents and they said no too. If you keep asking people and they all say no, but you still want that bike, what do you do?

This is kind of like what happens when people talk about additionality. They want to know if something is making a difference, or if it would have happened anyway. If you got the bike without asking anyone, that wouldn't be additionality because you didn't need to ask for help. But if you got the bike because your friend wanted to help you and gave you the money, that would be additionality because you needed the help to get the bike.

In the real world, additionality is often used when people want to see if a project or program is actually helping to solve a problem. For example, let's say a city government decided to build more bike lanes to make it safer for people to ride their bikes. But what if people were already riding their bikes a lot before the bike lanes were built? Then the bike lanes wouldn't be additionality because people were already doing what the bike lanes were supposed to encourage them to do. But if people started riding their bikes more after the bike lanes were built, that would be additionality because the bike lanes made a difference.

So basically, additionality is all about figuring out if something is really making a change or not. It's like trying to figure out if you really need help to get that bike or if you could have gotten it on your own.