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Current time:0:00Total duration:3:26

AP Macro: MKT‑4 (EU), MKT‑4.B (LO), MKT‑4.B.1 (EK), MKT‑4.B.2 (EK)

- [Instructor] In this
video we are going to use the GDP equation that we have seen before to think about how national
savings relates to investment. And really it's a way to
algebraically manipulate things to ensure that it fits with our intuition. So another way to think about a GDP is it's the same thing as national income, which we donate with a capital letter Y. And GDP or national income, we can account for it by saying, hey, that's going to be
the sum of consumption plus investment plus government
spending in a closed economy. We could also think about an open economy where you have net
exports right over here, but let's just focus on
a closed economy for now. So I'm gonna just actually label this. We're gonna deal with a
closed, closed economy. In a future video I will
open the economy up. But how could we solve for savings? Well, what happens if
we subtract consumption and government spending from
both sides of this equation? Well then you're gonna
have national income minus consumption, minus
government spending, is equal to investment. Now, what is another way of thinking about this left-hand side of this equation? So at a national level this is the income minus how much is being consumed and how much the government is spending. So it's income minus the
different types of spending. Well, you could view
this as national savings. National savings. And we see here this identity
that national savings, which is often denoted with a capital S, is equal to investment. And if that isn't
intuitive for you at first, just think about it at
a kind of human scale. If I am saving things and I
am putting it into a bank, that bank will then lend that money that can be used for investment. And we can break this down even more if we wanna think about taxes. So let's just say T is equal to taxes. So let's just think about
the private economy first. So if we think about the national income minus consumption spending, and then folks have
got to pay their taxes. So minus taxes. And then where do those taxes go? Well, they go to the government, so they stay in the economy. So notice, I'm not changing this equation, I'm just subtracting taxes
and then adding taxes. And then I subtract from
that government spending. These two equations are equivalent and this is going to be equal to our investment in our closed economy. Now, if you look at this
left-hand side right over here, you could view this as private savings. This is the national income, minus how much is being consumed, minus how much is being
paid to the government. So this is private, private savings. And if you look at the second part, the taxes the government gets minus how much the government spends, this you could view as public savings. Public savings. In most countries this
is neutral to negative, so it's actually the
public savings are negative 'cause the government spends more than the amount of revenue gets in taxes. But either way you could see the T minus G would be the public savings, and you add public savings
and private savings together, you get national savings.