<p>Because the supply of pounds in the model is controlled and fixed by the central bank. The central bank does not have to change (increase) the supply of pounds when the exchange rate changes. So the supply of pounds will be just a flat vertical line because no matter what the exchange rate is the supply of pounds will not respond to exchange rate as it is given by the central bank's monetary policy.</p>

CC BY-SA 4.0
2021-01-04T13:10:18.800Z
So the supply of currency in the foreign-currency exchange market is the same as the supply on the domestic money market? How does the Net Capital Outflow enter the picture then?
Jocka G
CC BY-SA 4.0
2021-01-04T13:23:21.553Z
@JockaG what do you mean? Central bank is the sole supplier of money in the economy some of it ends up on forex market.
csilvia
CC BY-SA 4.0
2021-01-04T14:41:53.247Z
Ok, I think I am a bit confused... I thought there were different money markets, one domestic one where the price is determined by an interest rate, and the other being the foreign-currency exchange market with the exchange rate as a price. Otherwise I am not sure what Mankiw and Taylor mean by saying that NCO determines the supply on the forex.
Jocka G
CC BY-SA 4.0
2021-12-06T08:41:03.060Z
@csilvia: Re: "Central bank is the sole supplier of money in the economy". Not true at all - see https://www.bankofengland.co.uk/-/media/boe/files/quarterly-bulletin/2014/money-creation-in-the-modern-economy.pdf
Mick
CC BY-SA 4.0
2021-12-09T10:43:47.817Z
@Mick you dont know what you are talking about. The question above is question about model with **exogenous** money supply (look at the money supply curve - it is vertical isn't it? Do you even know what that means?). That paper is about endogenous money creation in real economy, not about model with exogenous money creation. Please read the question,  before making off-topic comments.
csilvia
CC BY-SA 4.0
2021-01-04T12:50:15.417Z
2021-01-04T12:50:15.417Z
csilvia
<p>The authors assume that the capital outflow is exogenous, i.e. not affected by the current exchange rate. Here's why (from a U.S. point of view): <br/>If I want to invest money in Mexico, then I want to know how much money I get back after one year. That is determined by: the rate of return in Mexico (in pesos); and how much the peso/$ rate changes. Regarding the latter, it doesn't matter what the <em>current</em> exchange rate is; what matters is how much it will change in the coming year.</p>
<p>Of course, no one can predict exchange rate changes (similarly a rate of return usually can't be predicted, except for safe bonds). But those aren't relevant, because your chart simply shows that capital flows are not a function of the current exchange rate.</p>

CC BY-SA 4.0
2022-01-02T13:46:41.410Z
So why is only dollar supply due to asset purchases considered in the determination of equilibrium exchange rate. Why would the supply of dollars due to imports/exports be ignored?
Shaikh Ammar
CC BY-SA 4.0
2022-01-04T01:30:20.767Z
@Shaikh Ammar  Exports/imports are included in the blue downward-sloping line. Side note: this example assumes the country has a trade surplus. If the country had a trade deficit then: the demand for currency would be a vertical line, and an upward-sloping line would be the supply of currency.
Daniel
CC BY-SA 4.0
2021-02-05T02:52:32.483Z
2021-02-05T02:52:32.483Z
Daniel
<p>Let's assume an example of U.S. dollar in exchange for yen. I assume your rationale is that higher exchange rate would make people in the U.S. invest more in Japan because 1$ turned into more yen and thus more shares of Japanese stock. But you need to think that when you sell the Japanese stocks, you need to convert back to dollars. SO what really matter to net foreign investment is real interest rate differentials rather than real exchange rate. So Mankiw is right on this.</p>

CC BY-SA 4.0
2023-08-30T22:15:57.857Z
2023-08-30T22:15:57.857Z
Charlie Babe
<p>In the book 'Economics' by Mankiw and Taylor the demand and supply curves on the foreign-currency exchange market are shown as follows:</p>
<p><a href="https://i.sstatic.net/v7iOtm.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/v7iOtm.jpg" alt="the foreign-currency exchange market" /></a></p>
<p>The supply equals the Net Capital Outflow (NCO). I would have assumed that the exchange rate influences NCO in the same way it influences imports and exports, for example a higher exchange rate makes it more profitable to invest abroad than domestically, leading to an increased NCO. However, the supply isn't influenced at all by the exchange rate according to Mankiw and Taylor and that's what I don't understand.</p>

<supply-and-demand><open-economy-macro><foreign-exchange><nonexpert>
Why is the supply curve in the foreign-currency exchange market vertical?
Jocka G
# Why is the supply curve in the foreign-currency exchange market vertical?

(Asked by: username_0 on 2021-01-04)

In the book 'Economics' by Mankiw and Taylor the demand and supply curves on the foreign-currency exchange market are shown as follows:

[![the foreign-currency exchange market](https://i.sstatic.net/v7iOtm.jpg)](https://i.sstatic.net/v7iOtm.jpg)

The supply equals the Net Capital Outflow (NCO). I would have assumed that the exchange rate influences NCO in the same way it influences imports and exports, for example a higher exchange rate makes it more profitable to invest abroad than domestically, leading to an increased NCO. However, the supply isn't influenced at all by the exchange rate according to Mankiw and Taylor and that's what I don't understand.

**Tags:** supply-and-demand, open-economy-macro, foreign-exchange, nonexpert


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## 3 answers

### Answer by username_1 on 2021-01-04. Score: 1

Because the supply of pounds in the model is controlled and fixed by the central bank. The central bank does not have to change (increase) the supply of pounds when the exchange rate changes. So the supply of pounds will be just a flat vertical line because no matter what the exchange rate is the supply of pounds will not respond to exchange rate as it is given by the central bank's monetary policy.

> **Comments:**
> **username_0**: So the supply of currency in the foreign-currency exchange market is the same as the supply on the domestic money market? How does the Net Capital Outflow enter the picture then?  
> **username_1**: @JockaG what do you mean? Central bank is the sole supplier of money in the economy some of it ends up on forex market.  
> **username_0**: Ok, I think I am a bit confused... I thought there were different money markets, one domestic one where the price is determined by an interest rate, and the other being the foreign-currency exchange market with the exchange rate as a price. Otherwise I am not sure what Mankiw and Taylor mean by saying that NCO determines the supply on the forex.  
> **username_2**: @username_1: Re: "Central bank is the sole supplier of money in the economy". Not true at all - see https://www.bankofengland.co.uk/-/media/boe/files/quarterly-bulletin/2014/money-creation-in-the-modern-economy.pdf  
> **username_1**: @username_2 you dont know what you are talking about. The question above is question about model with **exogenous** money supply (look at the money supply curve - it is vertical isn't it? Do you even know what that means?). That paper is about endogenous money creation in real economy, not about model with exogenous money creation. Please read the question,  before making off-topic comments.  

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### Answer by username_3 on 2021-02-05. Score: 0

The authors assume that the capital outflow is exogenous, i.e. not affected by the current exchange rate. Here's why (from a U.S. point of view):   
If I want to invest money in Mexico, then I want to know how much money I get back after one year. That is determined by: the rate of return in Mexico (in pesos); and how much the peso/$ rate changes. Regarding the latter, it doesn't matter what the *current* exchange rate is; what matters is how much it will change in the coming year.

Of course, no one can predict exchange rate changes (similarly a rate of return usually can't be predicted, except for safe bonds). But those aren't relevant, because your chart simply shows that capital flows are not a function of the current exchange rate.

> **Comments:**
> **username_4**: So why is only dollar supply due to asset purchases considered in the determination of equilibrium exchange rate. Why would the supply of dollars due to imports/exports be ignored?  
> **username_3**: @username_4  Exports/imports are included in the blue downward-sloping line. Side note: this example assumes the country has a trade surplus. If the country had a trade deficit then: the demand for currency would be a vertical line, and an upward-sloping line would be the supply of currency.  

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### Answer by username_5 on 2023-08-30. Score: 0

Let's assume an example of U.S. dollar in exchange for yen. I assume your rationale is that higher exchange rate would make people in the U.S. invest more in Japan because 1$ turned into more yen and thus more shares of Japanese stock. But you need to think that when you sell the Japanese stocks, you need to convert back to dollars. SO what really matter to net foreign investment is real interest rate differentials rather than real exchange rate. So Mankiw is right on this.


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