 In a lot of the Ulversity Lessons about Health, you're going to see this term used quite a lot. Dowy. And it means something, you've probably already seen this, disability-adjusted life years. And what does that mean? Well, disability-adjusted life years are a measure of the health of a group of people or maybe the health of an individual, but generally it's for groups. And this is an indicator of how the health in a country is doing. And what it does is it takes a look at the health of a group of people and it basically puts it onto a lifeline. So how about we make a lifeline here? We'll start with a healthy life being in blue. So let's say our person is born and they're healthy for a couple of years here. Then they have some sickness for a while. So maybe they're sick here. And then they're healthy again for a little while. And then they're sick again for a while. Maybe they're sick here again. And maybe then at the end of their life, they die. Maybe they die a little early. So here we've got another little healthy bit. And here another little healthy bit. And then maybe they were sick right in the time before they died early. And let's imagine for the sake of argument that this back here is their life expectancy. So they were meant to make it to let's say 65 years in the country and society that they were in. So they're born here and they had these 65 years of life. But in reality they only made it to let's say this is 50. So immediately the math of Dali is going to count all of these years here as zeros. Or it's going to count them just not count them as a part of the healthy life span of this person. Then they're going to go back and take a look at these points in the calendar and the points in this person's life where they were sick. And they're going to give each one of those sicknesses a sort of a grade. And everything with Dali and it's sort of opposite which is Qali. Everything gets something that's kind of a one or a zero or somewhere in between. So let's say each one of these gets like a .5 for example. Many of them will probably get something like maybe a .7 or a .3. There's going to be lots of different numbers and they're a little bit deeper and more complicated than that. But what will happen is then these numbers will all be taken together. So all of these incidences of illness and then this incident of death will be taken together and added up into a big number. This number is the disability adjusted life years. And this is basically a count of how many life years someone lost to sickness or illness. Or to death actually as well. So of this 65 years how many years do people in a society actually really get in which they are healthy or how many are they losing to a disease. And this is actually really just a count of how much are we losing. Now one of the most amazing things about this entire topic is when you start taking a look at how much life people out there in the world are actually losing. So a study in 2000 that came out in 2005 was partially run by the WHO is one of the ones that you'll see quoted quite a lot in the current literature. And at that time the population of Africa was 655 million for Sub-Saharan Africa. And at that time the annual daily loss equals and be ready for this 358 million years. So for each year of life all the people in Africa are actually losing almost half of one in a way. Because if you look here there's this many people living their lives and there's this many lives, this many years of life being lost. So you think about that, that is a really staggering number. And the question is where does this come from? Well it comes from sickness, it comes from things like malaria. One of the really big causes is HIV because it has a very high dally score. It really takes a lot out of you. You also have TB. We've talked about these in other lessons but you have a number of other things. You also have things like hookworm, have anemia. You have lots of other things that are affecting the lives of people every day. So each year the entire continent of Africa is not able to produce, it's not able to live as much as they would if they were more healthy. And how much are they less able to live? Well this is kind of a hard number to imagine so I try to kind of quantify it. So I took this 358 million and I divided it out over 80 year lifespan. So if you were a healthy 80 year old then you would actually be able to live 400, 4.5 million lifespans. That's 4.5 healthy full 80 year lives are being lost in Africa and sub-Saharan Africa each year. Isn't that, that's really shocking actually. It's so shocking also when you think about it as being the population of a country like Ireland about the size of Ireland. So that is an incredible amount of productivity, that is an incredible amount of happiness, that's an incredible amount of just good days for people that they're just losing because they're not healthy. Now if you take a look at it on the global scale this is where it gets even more crazy. The same study found that 1.5 billion dallas are lost worldwide. Now if you take that and do the same math that I just did that's 19 million 80 year lifetimes. That is just a lot and if you kind of take a look at some populations of a few countries and you add them up that is actually the population of Sweden and Haiti combined. So if you were just to take those people and just wipe them off the earth that would be and actually if they were to live 80 year lifetimes which people in Haiti and Sweden don't do yet if you were to take those 80 year lifetimes and wipe them out that is the loss of life that's happening around the world every year. So that kind of hammers home I think some of the important aspects of Dali and why it is an important number. We are going to be talking more about Dali and lots of other things here in future lessons at alversity.org.