We Austrian economists are used to having terms corrupted, misused and redefined by statists and others who love and advocate strong central control of money and power. The term "inflation" is a prime example. We Austrians refer to "inflation" as creating new fiat money--as in inflation of the money supply. This is in sharp contrast to what we commonly hear in the mainstream media and from all Keynesian influenced economists, who use the term to describe a general increase in prices. Now nearly everyone thinks of inflation in this sense, so much so that we Austrians must always be careful to say "inflation of the money supply" whenever we use the term "inflation".
Those of us of a libertarian political persuasion, which includes many (but not all) Austrian economists, likewise bristle at how modern statists have hijacked and corrupted the term "liberal". Liberal is a term that is derived from the word "liberty". Ludwig von Mises even penned a book titled "Liberalism". Naturally, it contains not one reference to what today's so-called liberals advocate; i.e., erosion of property rights and statist intervention in almost all aspects of life.
However, now we Austrian economists are faced with a term that is new. It is NOT a term that has had a prior meaning and has been corrupted and re-defined.. It is a new, made up and wholly fabricated term-- "Negative Interest Rate".
Interest is founded on time preference
The rate of interest is founded on an innate trait of the human condition. All other things being equal, humans desire goods and services earlier rather than later. Austrian economists refer to this human trait as "time preference". Those who desire things sooner rather than later are said to have a high time preference. Likewise, those who desire things later rather than sooner are said to have a low time preference.
No two people have the same time preference. In fact, time preference changes within the same individual constantly. So someone with a higher time preference, but without the resources to own the good in the present, may be willing to pay others a higher overall price in the future for access to the good today; they may be willing to pay extra to use someone else's money in order to have it today. This "extra" is the interest rate that "someone else" will charge the person in order to allow the purchase to happen today.
Here you see a basic principle. There are TWO prices for something, a "have it now but can't afford it now price" and a "I'll save up to have it later price". The "have it now but can't afford it now price" means that the buyer must borrow--or we could call it "rent"--the money in order to buy it now. We call that "renting of money" interest.
The difference in price is the interest rate for that transaction at that place and time. One sees that there really is no single "interest rate". Like any market, what appears to be a price of a good--money, in the most common example--is constantly in flux due to the fact that it is derived from a human trait, time preference, that itself is constantly in flux.
Stop abusing our language and insulting everyone's intelligence
What the mainstream media and the public call a "negative interest rate" is an abuse of language. Time preference can never be negative, because that would require a total change in human nature. People will always want something sooner rather than later. It is HARD to save and delay consumption. People have to be disciplined to save and delay gratification. The idea of a "negative interest rate" is an attempt to turn reality on its head. It is another tactic in the Keynesian attempt to refute Say's Law; i.e., that production must precede consumption and that what one produces becomes the means by which he consumes. One can neither consume nor sell something that was never produced, which is the absurdity that is implied by a negative interest rate.
It is human nature that no one is willing to give up control of what he possesses now and accept less in the future. Since time preference can never be negative, the interest rate can never be negative. What is called a negative interest rate is merely a deposit charge that is difficult to avoid. Central banks throughout the world are exploiting their ability to charge for reserves held by their bank customers. By calling its charge a negative interest rate, central banks are trying to create the impression that what they are doing is a natural market phenomenon. It is no such thing. Because the central bank has a monopoly on the kind of money that may be used--its own!--and the quantity of money that people and businesses may use within a currency zone, it has the temporary power to force its member bank customers, and by extension its member banks' own customers, a fee for holding that which they cannot conveniently house anywhere else at the present time. This is nothing more than monetary repression, the purpose of which is to force the banks and their customers to loan, loan, loan, and spend, spend, spend respectively in order to re-inflate moribund economies.