La Bce e la trappola della liquidità

La Bce abbatte i tassi al 2% mettendo le mani avanti: "Non è nostra intenzione ritrovarci in una trappola della liquidità" (Jean Paul Trichet). Allude al fatto che a volte il costo del denaro può scendere fino a zero, senza avere alcun effetto di stimolo all'economia. In altre parole: "è possibile portare un cammello all'abbeveratoio, ma non lo si può costringere a bere", diceva Keynes. Che però l'espressione "trappola della liquidità" non l'ha usata nella Teoria Generale. La quale illustra nel capitolo XV "gli incentivi psicologici e commerciali alla liquidità". Eccone uno stralcio, a commento dei fatti monetari dell'oggi.

"We can sum up the above in the proposition that in any given state of
expectation there is in the minds of the public a certain potentiality towards
holding cash beyond what is required by the transactions-motive or the
precautionary-motive, which will realise itself in actual cash-holdings in a
degree which depends on the terms on which the monetary authority is willing to
create cash. It is this potentiality which is summed up in the liquidity function
L2. Corresponding to the quantity of money created by the monetary authority,
there will, therefore, be cet. par. a determlnate rate of interest or, more strictly, a
determinate complex of rates of interest for debts of different maturities. The
same thing, however, would be true of any other factor in the economic system
taken separately. Thus this particular analysis will only be useful and significant
in so far as there is some specially direct or purposive connection between
changes in the quantity of money and changes in the rate of interest. Our reason
for supposing that there is such a special connection arises from the fact that,
broadly speaking, the banking system and the monetary authority are dealers in
money and debts and not in assets or consumables.
If the monetary authority were prepared to deal both ways on specified terms in
debts of all maturities, and even more so if it were prepared to deal in debts of
varying degrees of risk, the relationship between the complex of rates of interest
and the quantity of money would be direct. The complex of rates of interest
would simply be an expression of the terms on which the banking system is
prepared to acquire or part with debts; and the quantity of money would be the
amount which can find a home in the possession of individuals who—after
taking account of all relevant circumstances—prefer the control of liquid cash to
parting with it in exchange for a debt on the terms indicated by the market rate of
interest. Perhaps a complex offer by the central bank to buy and sell at stated
prices gilt-edged bonds of all maturities, in place of the single bank rate for
short-term bills, is the most important practical improvement which can be made
in the technique of monetary management.
To-day, however, in actual practice, the extent to which the price of debts as
fixed by the banking system is 'effective' in the market, in the sense that it
governs the actual market-price, varies in different systems. Sometimes the price
is more effective in one direction than in the other; that is to say, the banking
system may undertake to purchase debts at a certain price but not necessarily to
sell them at a figure near enough to its buying-price to represent no more than a
dealer's turn, though there is no reason why the price should not be made
effective both ways with the aid of open-market operations. There is also the
more important qualification which arises out of the monetary authority not
being, as a rule, an equally willing dealer in debts of all maturities. The monetary
authority often tends in practice to concentrate upon short-term debts and to
leave the price of long-term debts to be influenced by belated and imperfect
reactions from the price of short-term debts;—though here again there is no
reason why they need do so. Where these qualifications operate, the directness of
the relation between the rate of interest and the quantity of money is
correspondingly modified. In Great Britain the field of deliberate control appears
to be widening. But in applying this theory in any particular case allowance must
be made for the special characteristics of the method actually employed by the
monetary authority. If the monetary authority deals only in short-term debts, we
have to consider what influence the price, actual and prospective, of short-term
debts exercises on debts of longer maturity.
Thus there are certain limitations on the ability of the monetary authority to
establish any given complex of rates of interest for debts of different terms and
risks, which can be summed up as follows:
(1) There are those limitations which arise out of the monetary authority's own
practices in limiting its willingness to deal to debts of a particular type.
(2) There is the possibility, for the reasons discussed above, that, after the rate of
interest has fallen to a certain level, liquidity-preference may become virtually
absolute in the sense that almost everyone prefers cash to holding a debt which
yields so low a rate of interest. In this event the monetary authority would have
lost effective control over the rate of interest. But whilst this limiting case might
become practically important in future, I know of no example of it hitherto.
Indeed, owing to the unwillingness of most monetary authorities to deal boldly in
debts of long term, there has not been much opportunity for a test. Moreover, if
such a situation were to arise, it would mean that the public authority itself could
borrow through the banking system on an unlimited scale at a nominal rate of
interest.
(3) The most striking examples of a complete breakdown of stability in the rate
of interest, due to the liquidity function flattening out in one direction or the
other, have occurred in very abnormal circumstances. In Russia and Central
Europe after the war a currency crisis or flight from the currency was
experienced, when no one could be induced to retain holdings either of money or
of debts on any terms whatever, and even a high and rising rate of interest was
unable to keep pace with the marginal efficiency of capital (especially of stocks
of liquid goods) under the influence of the expectation of an ever greater fall in
the value of money; whilst in the United States at certain dates in 1932 there was
a crisis of the opposite kind—a financial crisis or crisis of liquidation, when
scarcely anyone could be induced to part with holdings of money on any
reasonable terms.
(4) There is, finally, the difficulty (...)
in the way of bringing the effective rate of interest below a certain figure, which
may prove important in an era of low interest-rates; namely the intermediate
costs of bringing the borrower and the ultimate lender together, and the
allowance for risk, especially for moral risk, which the lender requires over and
above the pure rate of interest. As the pure rate of interest declines it does not
follow that the allowances for expense and risk decline pari passu. Thus the rate
of interest which the typical borrower has to pay may decline more slowly than
the pure rate of interest, and may be incapable of being brought, by the methods
of the existing banking and financial organisation, below a certain minimum
figure. This is particularly important if the estimation of moral risk is
appreciable. For where the risk is due to doubt in the mind of the lender
concerning the honesty of the borrower, there is nothing in the mind of a
borrower who does not intend to be dishonest to offset the resultant higher
charge. It is also important in the case of short-term loans (e.g. bank loans)
where the expenses are heavy;—a bank may have to charge its customers 1½ to
2 per cent., even if the pure rate of interest to the lender is nil".

da The General Theory of Employment, Interest and Money (Londra, 1936) Capitolo V, paragrafo 3.