1. Proportion of people who die due to violence/suicide. Bit tricky to define this rigorously. Does euthanasia count? Abortions? Starvation due to war? To market economics?

I’m not sure how applicable it would be to a hive mind species.

2. Power consumption as a proportion of total power emitted by their home star. Broadly captures technological development.

3. Fertility rate, counting only children who live to sexual maturity, with some adjustment for the number of sexes / sex ratio. Broadly captures how easy life is, at least after a certain level of development.

I’m not confident that 1 and 3 would even make sense in principle for all civilisations. And I’ve completely missed environmental considerations.

Wouldn't this bias development towards humanlike civilizations?

For example, if you measure income inequality, that presupposes a currency-driven labor market (as opposed to societies organized like ants and bees, or clonal organisms like some plants or siphonophores).

If you measure energy consumption or net primary productivity, it presupposes earth-like metabolism and industrial processes that derive useful work from stellar output. It's possible to imagine fusion-based civilizations, or highly efficient ones that have learned to manipulate gnomes and geological processes to suit their needs, but those wouldn't really be fairly captured by a crude measure of watts or calories.

Same with FLOPs, which is already a vague enough number even for human computing usages (with different outcomes / use cases requiring many different types and numbers of calculations), and makes things like analog or quantum computing harder to measure.

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I wonder if there's something more basic, like the ratio of information output (some unit of abstraction over various kinds of outputs, not only bytes but things like genomes and writing and music and art and other useful arrangements of energy and matter) divided by the energy available in a certain radius (a solar system? galaxy?) over time.

That lets you measure both ecological and technological outputs, allowing comparisons between humanlike societies, robot ones, fungal ones, maybe even geological ones (sentient volcanoes?), etc.

An interstellar species capable of great technological achievement. Yet with an attention span of a gnat requiring 1000s of civilisations to be summed up based on three numbers invariably influenced by my normative definition of 'civilisation state'.

Naively, I'd probably do approx age of civilization, lifespan of dominant species, and subjectively how technologically advanced the dominant species are.

If I could cheat and use bit twiddling to combine some into the same number, I'd probably like to capture things like average temperature, number of species, etc.

ok... but how would you measure technologically advanced? is there a concrete, measurable metric for it?

Just subjective rating from human perspective, I guess. I feel like any metric I'd come up with to try to capture it specifically could be thrown out the window by not knowing what I may encounter. What if they've figured something completely different out that doesn't involve transistors? Or even computation or electricity as we know it for that matter? Think of something like those creatures from Arrival, who just kinda looked like floating blobs but ended up being way more advanced than humans.

[ total number of soldiers, total energy of all weapons, supply cost per invading legion per day ]

Population growth rate. Globally, we're about 0.9%/year right now.

This is an interesting question but assumes that the interstellar species has the same motivations we do. Us showing a metric doesn’t mean they’ll interpret it the same way we do.

Possibly too broad but non-old-age death due to lack of resources (food, water, medicine, shelter, etc.) compared to surplus/deficit of those resources.

Attempting to show whether as a society we have the ability to stop those premature deaths and whether we’ve chosen to do so or not.

Maybe then also NEET (not in education, employment or training) relative to poverty rate? High NEET, low poverty means that AGI very likely exists. High NEET, high poverty means society is in trouble. Low/high means people are struggling to get by. Low/Low means things are likely somewhat efficient?