Behavioral finance FAQ / Glossary (Cascade)
This is a separate page of the C section of the Glossary
Dates of related message(s) in the
Behavioral-Finance group (*):
Year/month, d: developed/ discussed,
(Information / informational) Cascade, cascading
00/7i - 01/4i,9i,10i,12i - 02/1i,8i,9i - 03/6i,11i,12i
- 04/10i - 06/2i,3i + see (rational) expectations,
rational bubbles, crashes, trend, signal, noise,
reflexivity, beauty contest, percolation + bfdef2
The "If they do it, they must know something I don't know" syndrome.
Definition (in general) :
In general, an information cascade is a collective behavioral bias by which a superficial
(and often emotional) interpretation (availability cascade) of a minor event is spread
accelerated and amplified.
Definition (in markets)
A market-type information cascade materializes in a snowballing / cumulative
It starts with an initial price change that players interpret as
a signal that other players have relevant information.
It persists in a series (cascade) of self-reinforcing information / self-feeding
How does the market start the flow?
Do those guys really know something I don't know?
Or is it just what the water-tasting / cascade-rafting players believe?
An information cascade can start from a tiny buying or selling surge by some traders,
for good or bad reasons.
They are imitated by other players who suppose
that the first ones are better informed than them.
This first wave can launch repetitive moves in which most players imitate
one another instead of taking into account their own private information.
This gives a series (cascade) of self-reinforcing
information / self-feeding behavior
This phenomenon has some similarities with (see those words):
The "beauty contest", but without the divinatory element.
And it might be called ...ugliness contest when it sends price spiraling downwards,
"Herding" (but without the emotional content).
Other social epidemics and self-replicating phenomena in social communication :
viral communication, rumor, buzz, meme....
Short term and long term market cascades
How fast can the cascade get dry again?
A continuous trickle or avalanche (depending on its strength) of buying or selling
irrupts sometimes in financial markets.
It sustains a price trend, either upward or downward, temporary or
We have here a serial "positive feedback loops" (see the word "feedback"),
in which events get farther and farther from the mean, leading to a vicious (or
sometimes virtuous) spiral.
Actually, there are:
Many short term cascades, which usually abort soon
(often the day they started),
But also some medium / long term ones that
can reach extreme price lows and highs. Full overflow!
This happens when investor's emotions enter the game and reinforce what was at
the beginning only a feeble cognitive phenomenon (see below the section about
If the move becomes quite strong, it can even influence fundamentals in
a self-predicting way (see reflexivity, self fulfilling prophecy).
In financial markets, how is an information cascade
is triggered and how does it evolve into a spiral?
An ear on the rail, in case an incoming financial train
splashes a steam cascade
At its start, a financial information cascade can be triggered by a minor information,
which breaks through the surrounding "noise" and comes either from outside
(exogenous) or from inside (endogenous) the market
1) Cascade activated by (positive or negative)
(= coming from the economic sphere)
After this preliminary signal, market prices start moving, maybe
The cascade starts if this price move is taken as an endogenous signal
(= one coming from the financial sphere, in this case the asset market).
This convergence between exogenous and endogenous signals might start the
spiral - even in the lack of new confirmation from the economic sphere.
By the way, the economy also can be hit by self reinforcing phenomena.
They lead to economic development or decline in the long term, or to cyclical
expansion or depression in shorter periods.
Inflation spirals are another example, when people buy and hoard goods
by fear of inflation, contributing themselves to the price rise.
2) Cascade proceeding directly from an "endogenous"
info (from the financial market itself, a noticeable price
In this case:
1) The first information is a conspicuous market price rise or fall, in the
absence of any visible economic event than would explain it.
2) Some players take it as a signal that some other traders are buying
or selling because "they must know something that I don't know",
This is typical "noise trading" (see that phrase).
Somebody raises a little its voice, everybody does.
2b) Thus, they join the party and buy or sell in their turn.
Those actions reinforce the rise or fall, they add a second wave to it,
3) This new move brings a feeling among investors that the trend is confirmed,
It attracts even more people, who think there must be a good reason for it,
and tend to believe and spread the associated chatter, gossip and noise.
Those additional players start a third wave of rises or falls.
4) - 5) - X) Another wave of people sees that and act on
their turn, and things are cascading on and on.
Thus, even a lack of initial information by the first people who started
the trend can solidify into an information for the next ones who
saw them acting.
It shows that the trend can start out of nothing, when a pure noise
is taken as a signal (see noise, signal).
Technical analysis might play a part, when traders wait for a rise or fall,
as a signal that the trend is reverting, before they start to buy or sell.
Are information cascades rational?
Tactical followers sharing the shower.
In an information cascade, people decide consciously not to use their private
information and to act as "followers".
They deliberately consider the information that other players seems to know as more
relevantthan what they know by themselves.
They feel under-informed on fundamental facts. Thus they have
more trust in market price information, even if it is just
a noise or a slight adaptive market move.
Cascades vs. herding. And how persistent are they?
Flowing calculators? Or flowing cattle?
Cascades are sometimes called "rational herding". Is that definition justified ?
There is some rationality, cool
consciousness in information
cascades, even if it can be
called a perverse rationality.
Some even talk about rational
bubbles, rational crashes,
rational herding (hmm, why
not rational ...irrationality?
But when the momentum reaches
extremes, then greed, fear, pride,
envy and other
emotions come into play and
A typical emotional herding (see
To call cascades "rational herding"
can be justified in a first phase,
but no more once emotions take
Actually, without that emotional support,
the cascade does not reach the herding critical
threshold (see percolation) and aborts rapidly.
Information cascade that are not fed by emotion are fragile, as dispassionate people
soon start to check if there are some fundamental realities behind it, or if in fact
the king is naked. That is why,
People might obtain gains in that specific category of "trend-following",
based on the belief of hidden / private information.
This is one of the notions that is behind technical analysis.
But they might lose more than what they gained when the cascade music
stops and price trends start to revert or to go astray.
Look at that, some cascades flow upwards!
Here are examples of two opposite long term cascades,
a continuous stock market rise and a continuous stock market fall:
In a first step, a stock (or other asset) price rise happens at random, without any
relevant exogenous event (an effect of noise traders activity for example).
This rise is seen by some investors as a positive information.
They act on this belief. This initiates a new price rise, which in its turn attracts the
attention of other investors.
The steady arrival, every time there is a new rise, of new buyers who think
that those who bought just before them must know something, fosters a bullish
trend or even a bubble.
Cascades take place also in bearish trends and in crashes.
Some first investors get weary or cautious, even if no relevant new event takes
place to cause it.
Under such an impression, they leave the game. They are then followed by others.
This is how Crashes usually start out of the blue, without new exogenous
This does not mean there are no reasons at all, as overpricing is usually the
But the precise moment when the market will act on that reality is rather
unpredictable, there are often no discernible early warnings that the party
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