Where does bubble collide?

A large and sustained rise of an asset's market price above the value its fundamentals would justify, driven by expectations of further gains rather than by the underlying cash flows. Scherbina and Schlusche's 2014 Asset price bubbles: a survey reviewed how such deviations are defined, how they are said to form and grow, and how difficult they are to identify while they last. The referent is a mispricing in a market, a gap between price and estimated fundamental value, and it has nothing to do with a cavity in a liquid, a gap in what a person reads, a sorting procedure, or a closed group of contacts.[1]

Unit

A sustained gap between an asset's market price and its estimated fundamental value

Recovery means

The gap closes when the price falls back toward fundamentals, often abruptly, in what is usually called a crash

Measured by

Inferred by comparing prices to present-value estimates of fundamentals, or by statistical tests for explosive price dynamics

A social structure for sharing knowledge in which some relevant voices are left out, not by active exclusion but by omission, so members are simply never exposed to the sources that would challenge them. Nguyen's 2020 Echo chambers and epistemic bubbles drew a sharp line between this and an echo chamber, arguing that an epistemic bubble is a mere coverage gap that bursts once the missing evidence is encountered, whereas an echo chamber actively discredits outside voices. The referent is a gap in whose testimony reaches a person, and it is unrelated to a cavity in a liquid, a market mispricing, an algorithm, or an epidemiological contact group.[2]

Unit

A knowledge-sharing network that omits relevant sources, leaving members underexposed to challenge

Recovery means

It bursts easily; exposure to the omitted evidence is usually enough to correct it, which is what separates it from an echo chamber

Measured by

Assessed by mapping whose sources and testimony a person is, and is not, exposed to

A simple comparison sort that steps through a list again and again, comparing each adjacent pair and swapping them when they are out of order, so that on each pass the largest remaining value rises, or bubbles, to its place at the end. Astrachan's 2003 Bubble sort: an archaeological algorithmic analysis traced the name and the method and examined why the algorithm persists in teaching despite its poor efficiency of order n squared. The referent is a procedure over data, counted in comparisons and swaps, and it names nothing in common with a market bubble, a gas cavity, an information gap, or a group of people.[3]

Unit

A sorting procedure over a list, described by its comparisons and swaps, of order n squared

Recovery means

Not applicable

Measured by

Analysed by counting the comparisons and swaps it performs, giving worst-case and average-case time of order n squared

A small, closed group of people who agree to keep close contact only with one another, so that an infection reaching one of them cannot easily spread beyond the group. Block and colleagues' 2020 Social network-based distancing strategies to flatten the COVID-19 curve in a post-lockdown world modelled such strategies on contact networks and compared how different ways of forming groups affect transmission. The referent is a bounded set of contacts chosen to slow a disease, counted by its members, and it shares only the word with a market bubble, a gas cavity, an information gap, or a sorting routine.[4]

Unit

A closed group of people who restrict close contact to one another, by the number of members

Recovery means

Not applicable

Measured by

Studied by simulating transmission over contact networks and comparing rules for how the groups are formed