The case for reducing existential risk

"In the course of the last four months it has been made probable — through the work of Joliot in France as well as Fermi and Szilárd in America — that it may become possible to set up a nuclear chain reaction in a large mass of uranium, by which vast amounts of power and large quantities of new radium-like elements would be generated. Now it appears almost certain that this could be achieved in the immediate future. "This new phenomenon would also lead to the construction of bombs, and it is conceivable — though much less certain — that extremely powerful bombs of a new type may thus be constructed. A single bomb of this type, carried by boat and exploded in a port, might very well destroy the whole port together with some of the surrounding territory. However, such bombs might very well prove to be too heavy for transportation by air."

Einstein–Szilárd letter, Wikipedia, Archived link, retrieved 17 October 2017. ↩︎

Nick Bostrom defines an existential risk as event that “could cause human extinction or permanently and drastically curtail humanity’s potential”. An existential risk is distinct from a global catastrophic risk (GCR) in its scope – a GCR is catastrophic at a global scale, but retains the possibility for recovery. An existential threat seems to be used as a linguistic modifier of a threat to make it appear more dire. ↩︎

Greenberg surveyed users of Mechanical Turk, who tend to be 20-40 and more educated than average, so the survey doesn’t represent the views of all Americans. See more detail in this video: Social Science as Lens on Effective Charity: results from four new studies – Spencer Greenberg.

The initial survey found a median estimate of the chance of extinction within 50 years of 1 in 10 million. Greenberg did three replication studies and these gave higher estimates of the chances. The highest found a median of 1 in 100 over 50 years. However, even in this case, 39% of respondents still guessed that the chances were under 1 in 10,000 (about the same as the chance of a 1km asteroid strike). In all cases, over 30% thought the chances were under 1 in 10 million. You can see a summary of all the surveys here.

Note that when we asked people about the chances of extinction with no timeframe, the estimates were much higher. One survey gave a median of 75%. This makes sense — humanity will eventually go extinct. This helps to explain the discrepancy with some other surveys. For instance, “Climate Change in the American Mind” (May 2017, archived link), found that the median American thought the chance of extinction from climate change is around 1 in 3. This survey, however, didn’t ask about a specific timeframe. When Greenberg tried to replicate the result with the same question, he found a similar figure. But when Greenberg asked about the chance of extinction from climate change in the next 50 years, the median dropped to only 1%. Many other studies also don’t correctly sample low probability estimates — people won’t typically answer 0.00001% unless presented with the option explicitly.

However, as you can see, these types of surveys tend to give very unstable results. Answers seem to vary on exactly how the question is asked and on context. In part, this is because people are very bad at making estimates of tiny probabilities. This makes it hard to give a narrow estimate of what the population in general thinks, but none of what we’ve discovered refutes the idea that a significant number of people (say over 25%) think the chances of extinction in the short term are very, very low, and probably lower than the risk of an asteroid strike alone. Moreover, the instability of the estimates doesn’t seem like reason for confidence that humanity is rationally handling these risks. ↩︎