Offense-defense capital and other costs remain stable over time despite and independent of technological changes.

An intriguing question/observation.  From The Offense-Defense Balance Rarely Changes by Maxwell Tabarrok.  

The disagreement here hinges on whether a technology will enable offense (bioweapons) more than defense (vaccines). Predictions of the “offense-defense balance” of future technologies, especially AI, are central in debates about techno-optimism and existential risk.

Most of these predictions rely on intuitions about how technologies like cheap biotech, drones, and digital agents would affect the ease of attacking or protecting resources. It is hard to imagine a world with AI agents searching for software vulnerabilities and autonomous drones attacking military targets without imagining a massive shift the offense defense balance.

But there is little historical evidence for large changes in the offense defense balance, even in response to technological revolutions.

Consider cybersecurity. Moore’s law has taken us through seven orders of magnitude reduction in the cost of compute since the 70s. There were massive changes in the form and economic uses for computer technology along with the increase in raw compute power: Encryption, the internet, e-commerce, social media and smartphones.

The usual offense-defense balance story predicts that big changes to technologies like this should have big effects on the offense defense balance. If you had told people in the 1970s that in 2020 terrorist groups and lone psychopaths could access more computing power than IBM had ever produced at the time from their pocket, what would they have predicted about the offense defense balance of cybersecurity?

Contrary to their likely prediction, the offense-defense balance in cybersecurity seems stable. Cyberattacks have not been snuffed out but neither have they taken over the world. All major nations have defensive and offensive cybersecurity teams but no one has gained a decisive advantage. Computers still sometimes get viruses or ransomware, but they haven’t grown to endanger a large percent of the GDP of the internet. The US military budget for cybersecurity has increased by about 4% a year every year from 1980-2020, which is faster than GDP growth, but in line with GDP growth plus the growing fraction of GDP that’s on the internet.

This stability through several previous technological revolutions raises the burden of proof for why the offense defense balance of cybersecurity should be expected to change radically after the next one.

The stability of the offense-defense balance isn’t specific to cybersecurity. The graph below shows the per capita rate of death in war from 1400 to 2013. This graph contains all of humanity’s major technological revolutions. There is lots of variance from year to year but almost zero long run trend.

Click to enlarge.

Does anyone have a theory of the offense-defense balance which can explain why the per-capita deaths from war should be about the same in 1640 when people are fighting with swords and horses as in 1940 when they are fighting with airstrikes and tanks?

There is something definitional here.  We know (The Better Angels of Our Nature by Steven Pinker, Constant Battles by Steven A. LeBlanc) that deaths from societal violence have declined dramatically over the historical record.  It is tiny now compared to 500 or 1,000 years ago.    That does not match the trend lines above.

My suspicion is that Roser's definition of death from violent conflict is somehow constricted to interstate conflict deaths versus state and non-state violent deaths.  The distinction is worth clarifying but I take the broader point.  That the capital costs associated with state level violent death maintains a surprising and unexpected steadiness over decades and centuries.  There seems almost some homeostatic interplay between technology, economics, and state driven deaths.