No, you have this all backwards. Let's take a hypothetical country -- Fredonia with it's Fredonian Franc. The government of Fredonia decides "I want to be a global reserve currency!". How would they go about accomplishing that?
First, let's define what it means to be a global reserve currency. What it means is that other reserve banks use your currency as their reserve. That means other reserve banks need to accumulate Fredonian Francs, and in large amounts.
Of course banks don't warehouse currencies, they would be holding Fredonian Government Bonds (FGB), which must be bought with Fredonian Francs. So how would they get their hands on large numbers of FGBs? By running trade surpluses against Fredonia.
In other words, to be a reserve currency means you have to allow the rest of the world to run large trade surpluses against you, which means you have to allow your currency to be permanently overvalued relative to the rest of the world -- relative to what it would be valued if there was no global investment demand for Fredonian Francs.
Now, all of a sudden, it's not looking like such a great proposition for the Fredonians, as this means that their own production is disadvantaged in global markets more or less permanently and their financial system has to be huge and swollen. It distorts the Fredonian economy and hurts workers. That would require a very resilient economy and a population willing to tolerate the employment hit to running persistent trade deficits vis-a-vis the rest of the world.
Next, Fredonia would need to develop deep and liquid capital markets, so that the rest of the world would be confident in storing their wealth there. That means a long tradition of rule of law, large turnover at low prices, and huge bond markets. Big enough to absorb the surplus of the entire world. It also means that your interest rates are going to be permanently lower than they would be if there was no excess global demand for FGBs. This means your economy is going to be subject to asset bubbles and financialization -- we're talking huge bond markets that risk dominating the country.
So the economy of Fredonia has to be big, be investor friendly, have strong property protections and rule of law, a grotesquely bloated and powerful bond market, and be willing to run permanent trade deficits vis-a-vis the rest of the world.
Not many nations qualify on all of these accounts, right? China is big enough, but no rule of law, and since their entire economy is based on running trade surpluses instead of trade deficits, they are suited to be the accumulator of global reserves rather than the issuer of global reserves. Saudi Arabia? Nope. The EU? Nope. Simply no one else is both able and willing to pay the price to be a global reserve currency, and that's why it's going to remain the USD. Not only is this not a "fickle" thing, the rest of the world should be grateful that the US is willing to sacrifice the interests of its own workers and production base in order to make sure the rest of the world has a steady supply of USG bonds.
Rather, the real question is how long will the US be willing to bear this burden? When the US was 40% of global GDP, and global trade was tiny relative to global GDP, it didn't seem like a very big burden. But today, when the US economy doesn't dominate the rest of the world and trade is huge, the price of being a global reserve currency is devastating. It means de-industrialization, collapsing cities in the rust belt, rising death rates and a shrinking US middle class, as well as rising Federal deficits.
I can very easily see a future in which the US starts imposing more and more capital controls that prevent foreigners from purchasing dollar assets similar to protections that other nations have, at which point guess what -- there will be no global reserve currency. The free ride, for the rest of the world's producers, will be over.
Trade agreements will need to go back to being settled either bilaterally, or with some kind of specie (gold? silver? bitcoin?). This would be a great thing in some respects, because it would force each nation to not overproduce, but it would cause a huge contraction in international trade, corresponding to a contraction in global GDP and well being, and especially to those economies that rely on running persistent trade surpluses in order to employ their workers -- nations such as Germany, China, Japan will take big hits should they lose the ability to persistently run surpluses.
This would also imply that the Fredonian government would be highly incentivized to run at a constant deficit, more so than other governments, because its cost of capital would be lower.
Your argument is so convincing that I am having a hard time seeing what the US gets out of all this. Cheaper capital and cheaper imports, I suppose. But surely there is a reason for this besides American altruism.
But if the US ever gets tired of this, why would it start capital controls? Why not just inflate the currency?
This is the same reason why a policy of "inflating the currency" is not going to work for the US, and instead capital controls are the policy option of choice. I don't want to get the goldbugs in this thread, but the quantity of money is demand determined by the private sector, and the policy variable that the government has is the overnight interest rate. This means that "inflating the currency", or trying to create inflation, is done by lowering the policy rate. Fighting inflation consists of raising this rate. So when you say "inflate the currency", what you mean is lower the rate of interest. But that rate can only be lowered to zero, and more importantly other nations will respond by lowering their interest rates. This process is called "competitive devaluation", because what matters for the trade balance is the relative value of the dollar with other currencies, not the absolute value. The US cannot unilaterally set the relative value, and devaluation by US will be met with devaluation by our trading partners.
Moreover devaluation is very risky and might substantially increase the trade deficit, because when the rest of the world devalues their currency to match, it is much more likely that they are the ones who will suffer a currency crisis than the US. So this policy would risk destabilizing the currencies of our trading partners, leading to financial crisis and another flight to the USD as a safe haven as investors flee the currencies of our trading partners and rush to the US.
On the other hand capital controls is something that can be done unilaterally and cannot be countered in the same way as competitive devaluation. If we impose a tax, of say, 2% on foreign holders of US assets, and the rest of the world retaliates with their own tax, then this is unlikely to cause a global currency crisis, it will cause cross border capital flows to suddenly reverse in which US investors pull their money out of foreign nations while foreign investors pull their money out of the US and bring it back home. Because foreigners invested more in the US than the other way around, this should result in more capital flowing into the rest of the world rather than the kind of capital flight that creates a currency crisis.
In terms of how we got to this point, that's a tough question because you are asking me to assert motives and plans, when all I can reliably do is describe the current situation we are in. If I were to guess, I think it was not intentional. When the UK was the dominant economic power and the pound was the reserve currency the UK also suffered from chronic trade deficits, but the size of the imbalances were so much smaller before WW1 than today. What is happening now is truly unprecedented in the economic history of the world -- the depth of global supply chains, and the size of global trade imbalances is not something anyone would have predicted. So my guess is that the US maintained open capital markets for political and historical reasons -- because England did, and because market liberalism was a dominant economic philosophy. The US maintained rule of law for similar cultural and historical reasons. Then, after WW2, ours was by far the dominant economy, and everyone wanted to invest their assets in the US, particularly when the rest of the world was in shambles after WW2. It's said that the Marshall plan -- that transfer of dollars to Europe -- only partially offset the flight of money from Europe to the US as people wanted to invest in our bonds because we were a safe haven. So I would say that's how we became a reserve currency.
But in the beginning, the amounts were so small relative to the size of our economy that it didn't disrupt anything.
Over time, it did begin to disrupt things, but perhaps the benefits outweighed the costs to the people who mattered. Those working in US capital markets benefit from this system, since they get a cut of the transactions. And there is still a contingent of die hard market liberals who insist that we must maintain open capital markets, even as the rest of the world takes advantage of this.
Then businesses benefit, in the short term, from outsourcing. Consumers benefit, to some degree, from cheaper imports. The lower interest rates cause asset prices to be higher, so houses are more expensive as are stocks. This benefits the generation that bought the assets when they were cheaper.
So it's not the case that the entire nation is a loser. There are constituencies that benefit from this system and they have power. However the costs are mounting, and the benefits are fading. It's great to have a huge increase in house prices, but that's a one time hit -- a transfer to one or two generations. For the generations that come after, housing is just more expensive. It's great to have boosted stock prices from outsourcing, but now US firms are discovering that they have foreign competitors who are climbing the value the chain.
And of course the social costs for working class Americans are devastating, leading to political instability. I think we are well past the point where the benefits outweigh the costs.
By the way, I am not predicting that we adopt capital controls -- such a thing would be unheard of for us, since we are so indoctrinated in believing that free flow of capital is a type of virtue. However I am a believer in the principle that unsustainable things at some point must end. We cannot continue to bear this burden indefinitely.
so yeah, i don't buy it. the US isn't 'saving the world' by holding the dollar as a reserve. the entire US economy is hanging on by a thread and would collapse if they lose the global trade commission on dollar.