|Dreaming of Immortality in a Thatched Cottage - 1500s|
Exogenous/endogenous money, reflux, hot potato money, helicopter money, inelastic vs elastic currency. These are all part of the colourful lexicon developed by monetary economists over the centuries to outline a general set of problems: how does money get emitted from source, and when, if at all, does it return to source?
We usually describe money as exogenous, hot potato, helicopter, or inelastic if it is emitted at the initiative of the issuer, and the issuer doesn't allow the public to exercise any initiative in returning this money back to source. Once it has been air-dropped into circulation from a helicopter, this kind of money becomes immortal, passing like a hot potato from person to person forever.
We describe money as elastic or endogenous when the money-using public exercises its own initiative in both drawing money out from an issuing source and pushing (refluxing) this money back to the source. This sort of money never strays far from its issuer, snapping back like a rubber band to be destroyed when it is no longer wanted. Rather than being a hot-potato zombie, elastic money lives fast and dies young.
There's a big debate among monetary economics about whether money is exogenous/hot potato/helicopter/
I find it helpful to skirt around the skirmish and re-orientate the debate around finance, not monetary economics. This means that we've got to translate the language of monetary economists—hot potatoes, exogenous/endogenous, reflux, and the like—into the lexicon of financial instruments.
Let's head over to the stock market first. I'm going to hypothesize that the common stock is a thoroughly exogenous financial instrument. A firm decides when to issue new stock and at what price. Once stock has been issued, there's no way for an investor to automatically return the stock to the issuer. Stock wanders zombie-like through the financial world until the issuing firm is wound up, if ever. General Electric's original 1000 shares, for instance, have been hot-potatoing through financial markets since June 23, 1892.
Also found on stock markets are exchange-traded funds, or ETFs. Unlike stocks, though, I would say that ETFs are thoroughly endogenous financial instruments. Take the SPDR Gold Trust ETF. When investor demand for the Gold Trust heats up, ETF units will trade at a premium to their implied gold value. Large authorized-participants buy units from the ETF originator at par, paying with gold, and then sell these blocks to the public until the premium has disappeared. Vice versa when GLD units are at a discount to their real gold value. Now the authorized-participants buy units from the public at a depressed price and sell them to the ETF originator at par for gold. The result is that the quantity of outstanding units fluctuates quite widely, as the chart shows, but the price, specifically the premium/discount, stays constant. The public, through the intermediation of authorized-participants, sucks out whatever quantity of ETF units from the issuer that it desires, and then refluxes unwanted units back to it.
Unlike ETFs, bonds are exogenous financial instruments. Firms issue bonds when they need funding and these instruments stay outstanding until redemption date or firm instigated early-retirement. Until then, bonds pass hot potato-like from hand to hand in the secondary market.
Not all bonds are like this though. A retractible bond, or retractible debenture, is a different beast. Investors can choose to exercise the retractibility feature of this species of bond and force its issuer to buy it back. If we break down a retractable bond into its parts we see that it is a bond with an embedded put option. The put allows investors take the initiative and "reflux" the bond back to the issuer.
Retractability, or puttability, is a feature that gets often gets added to preferred shares and sometimes even common stock. The interesting thing about retractibility and puttability is that it turns what was once an exogenous hot potato asset into a semi-endogenous instrument. While investors can not "pull" retractible bonds or puttable stock out of an issuer, they can easily push, or "put", already-issued retractibles back to the issuer when those instruments are no longer desired.
How can we turn our semi-endogenous retractible bond or puttable share into a fully endogenous instrument? Let's consider another financial instrument, the gift card. Indigo, a bookstore up here in Canada, allows consumers to buy any quantity of gift certificates at the till. These gift certificates are puttable—their owner can immediately return the card for redemption. That the public can take the initiative in both buying unlimited amounts of gift cards and returning those coupons whenever they want qualifies them as fully endogenous. Not only is the "discount window"* for endogenous instruments like puttable gift certificates and ETF units always open, there is also a well-defined rule for pricing the emission of new units. Retractible bonds, which already have the put feature, would qualify as fully endogenous if their issuer were to set up a "window" with a set of rules so that investors could draw out new bonds on their own accord.**
Because endogenous and exogenous instruments are structured differently, they act in peculiar ways when market conditions change. When the demand for an exogenous instrument like GE stock increases, its price will quickly rise to meet that demand while its quantity stays fixed. When demand falls, the only way for investors to rid themselves of GE is to bid its price down until it reaches a real value at which the market willingly holds it. Things work differently with endogenous instruments. When the demand for an endogenous instrument like a coupon or gift certificate increases, its quantity quickly rises whereas its price stays fixed. When demand falls, investors can exercise their put option and send them back to their issuer. In sum, prices do all the work in exogenous adjustment whereas quantities do all the work with endogenous adjustment. Exogenous issuers can choose the quantity of their issue, but not the price, whereas endogenous issuers can choose the price but not the quantity.
So back to the great debate. Is money endogenous or exogenous? If money is defined as a certain narrow set of financial instruments (cash + deposits, M1, M2, whatever) then we need to appraise each instrument's structure to see whether its issuer provides an associated discount window and embeds a put option—or not. A quick glance through the instruments found on the narrowest lists of money (say M1) shows that almost all of these instruments have embedded put options and discount windows, so narrow money is primarily endogenous.
This is different from a few centuries ago when gold and silver constituted a significant share of the narrow money supply. Since the only way to get rid of an ounce of metal is to pass it on, gold, like stock, is exogenous and immortal, with the very same gold coin once used 5000 years ago still circulating today, though perhaps in bar form. Modern monetary economists are beginning to add exogenous assets like t-bills, bonds, and other AAA-rated debt securities to the list of money since these assets can be easily collateralized. In doing so, economists are slowly returning to a world in which a larger percentage of the assets on the list of money are exogenous.***
And finally, there's the moneyness, or liquidity, view. From this perspective, there is no limited list of money-items. Rather, all assets provide varying degrees of money-services. Put differently, moneyness is a vector which spans all assets. Because it inheres to a degree in all assets, moneyness is both endogenous and exogenous. After all, the universe of assets is comprised of both types of assets. A change in the demand for liquidity/moneyness results in a complex shift in prices and quantities. Liquid endogenous instruments are drawn out of issuers and less-liquid endogenous instruments refluxed back to issuers. Liquid exogenous instruments rise in price while less liquid exogenous instruments fall in price.
*In modern days, the discount window refers to a central bank's ability to lend. In the old days, banks had actual "windows" behind which stood a bank officer who would accept securities in return for bank deposits or cash. A "discount" to its market value was applied to the securities, a sort of haircut that also provided the banks with income. See this image from the Philly Fed.
**A bank deposit is the quintessential endogenous instrument. There are multiple windows for buying a deposit -- one can either sell cash to get deposits, or sell personal IOU to get them, with each window offering different rules and rates. When deposits are no longer needed, one can "put" them back at any point by requesting cash or a return of one's personal IOU.
***With the emergence of Bitcoin, Ripple XRPs, and the other alt-currencies, we're seeing the return of exogenous monies with a vengeance.
Note: For more on reflux, I'd definitely recommend Mike Sproul's The Law of Reflux. For more on exogenous money, Nick Rowe is who you should be reading.