"Give me back my money!" shouts young Michael Banks at the greedy Mr Dawes, the old banker who has snatched his tuppence out of his hand. A fatal act of rebellion: the depositors think the bank will not repay their deposits, and panic breaks out in the lobby. "Be quick, young man, all the money in my account!" The wealthy ladies in the queue lose their poise and pound their fists on the counters. The crowd breaks down the main doors. Within seconds the management stops all payments and has the pounds locked away in the vault.
With this scene, exactly one minute long, Mary Poppins, Disney's 1964 masterpiece, managed to explain the fragile balance on which the financial system rests: trust. Trust in the fact that banks will always be able to meet their obligations and repay anyone wishing to withdraw their money. Only a tiny percentage (less than 2%) of what is deposited is actually kept by the bank in cash or in easily liquidated assets (the so-called "fractional reserve"). A charade, a dangerous but necessary fiction.
All banks, in every part of the world, work this way, because keeping only a small share of the money on deposit is instrumental to the granting of credit.
But what happens if everyone asks to withdraw their holdings at the same moment? This is the classic case of a bank run, precisely that notorious rush to the counters in the Disney classic: the bank cannot satisfy the demands of all its customers with its fractional reserve, and it fails.
It is clear, then, how essential a role trust plays in this story. The depositor must trust the bank, must be convinced that their money is always ready to be withdrawn and used. Must believe, ultimately, that the institution is healthy enough to protect their savings.
When this reliance vanishes or fades – at the cry of a child, which is itself the metaphor for a suspected insolvency – the natural impulse is to put one's money out of harm's way. And so to withdraw it, to entrust it to others or keep it in private hands. With a train of dire consequences: the worsening of the institution's economic crisis, which loses any chance of recovering on its own (it is like beating a man already on the ground); the possible contagion of other institutions, smaller or connected (because while trust spreads only with difficulty, mistrust is instead highly contagious); the loss of prestige and solidity of the whole banking system.
For this reason there are various instruments designed to increase the market's overall confidence in the "custodians" of wealth. First among them, the deposit guarantee scheme which, in Italy, protects current accounts up to 100,000 euros in the event of a bank's insolvency. More generally, the "political" reassurance, on the part of governments and central banks, that an institution will never be allowed to fail and drag depositors' savings into the abyss (in our country they are safeguarded by the Constitution as well). A guarantee so strong that it has in fact been provided even by the current, populist-leaning Italian government, despite its earlier criticism of the practice of "bailing out the banks".

In the Mary Poppins film, the run on the bank produces at least one other bitter effect: poor Mr Banks, a partner in the Bank of London and father of the little rascal, is summoned before the board of directors and dismissed. In the background, the fog and the silence of an England on the eve of the Great Depression.
Very different is the atmosphere that sets the stage, in 2007, for another colossal episode of bank run, this time a real one. When the customers of Northern Rock, one of the largest British banks, begin to doubt its financial soundness, they set off en masse towards the branches to withdraw their deposits. The queues that form are, in the British style, composed and orderly. But the consequences too are the usual ones: Northern Rock is brought to its knees and the government has no choice but to nationalise it. Similar scenes have at times affected entire countries, such as, in the new millennium, Argentina, Uruguay and Greece. When it is trust in a nation that gives way, the run on the banks is general. After all, in the financial sector too panic is a self-feeding phenomenon ("the only thing we have to fear is fear itself", said Franklin Delano Roosevelt).

In the United States the greatest financial crises, usually following a period of economic expansion, are remembered as "The Panic". That of 1837, of 1857, or again that of 1907. By way of the "Panic of 1893", which inspired Dazey's melodrama "The War of Wealth", whose playbill has become the iconographic symbol of the phenomenon. And it is precisely to those years that the scandal of the Banca Romana belongs. The episode made the Giolitti government fear a cascade effect on the Italian system, and the inquiry by Alvisi, President of the Court of Auditors, was at first kept hidden. But the cover-up did not last long: thanks to the efforts of the member of parliament Colajanni, the report of denunciation was deepened and made public, and for a whole year the national debate was dominated by the affair. In his inspections Alvisi had uncovered the misdeeds of Governor Tanlongo and his circle. To make up for an over-generous lending business, the Banca Romana had begun assigning the same serial number to several banknotes: some were withdrawn as "worn out" and then put back into circulation together with the duplicates. A sensational case of misplaced banking trust, which would give rise to the Bank of Italy and to a stricter system of controls.

In the Mary Poppins sequel, in cinemas last December, Michael Banks is by now a family man contending with the new director of the Bank of London, an unscrupulous Colin Firth. This time the institution is ready to wrest from him the ownership of his home, mortgaged because of financial troubles. Once again it will be Poppins, back on the offensive at the helm of her umbrella, who saves the whole show. So, once more, an anti-bank nanny. A communist, as the collective The Fraser wrote in Mary Poppins: song, dance and latent socialism (2016)? Perhaps that is too much. A fine economist, certainly.

"Not just credit, in that film there is Keynes and happy degrowth"

It all begins with the Book of Genesis and with Pinocchio. One day Sergio Sacchi, who teaches macroeconomics at the University of Perugia, decides to read those stories through the lens of his subject. Taking a liking to it, he goes on with Cinderella, Robinson Crusoe, Aesop, Heidi and, of course, The Wizard of Oz, with its emerald-green (or dollar-green!) city and its golden bricks. And so takes shape "Economics and Fairy Tales", a successful talk with which Sacchi has already entertained various audiences around Umbria. In the professor's round-up there is room for Mary Poppins too.

Sacchi, what does the "perfect" nanny tell us about economics?

"The bank scene is a classic by now, but I have read other things into it as well. In Travers's book, Mrs Banks gives up a better house in order to have more children, and already here the Keynesian theories of preference appear. But then there is the child who, instead of investing his little coin, wants to use it to feed the pigeons: almost a metaphor for today's debate on "happy degrowth" and "gross domestic happiness"".

The joy of living against the grey bankers: was Mary Poppins left-wing?

"Her approach to reality was certainly an optimistic one: to face the storms of life (financial ones included) with a supercalifragilisticexpialidocious. But it is wrong to reduce everything to ideological Manichaeism, because every story has its own historical context. When I was a boy people even wondered whether the Gospel was communist or socialist: absurd!

After all, Walt Disney was accused both of being pro-communist and of being a McCarthyist.

Exactly. A confirmation of how misleading it is to seek univocal answers to complex situations".

Will this talk become a book?

"I don't think so: knowing me, it would come out as an encyclopaedia. For now I enjoy sparking the curiosity of a live audience and watching its enthusiasm".

And do you use fairy tales with your students too?

"Sometimes, yes: young people need constant stimulation. But I warn them at once: I may well talk about fairy tales, but at the exams I give no discounts!".

Do populism and economic crisis influence the atmosphere in university lecture halls?

"The average student is ever more conditioned by today's individualism: I would not be surprised if, faced with a failing grade, someone were to tell me that they do not share "my view of things"".

In the end, what is the aim of your lectures? To reveal an economic moral behind every story, or simply to popularise a complicated subject by drawing on imagination?

"This and more. But above all to send a small pedagogical message: to invite adults to reread the classics with the eyes of today. To become children again, but with the sense of balance of grown-ups".

Giovanni Landi holds a PhD in Legal Sciences. He is currently a trainee journalist at the Centre for Radio and Television Journalism in Perugia.