I suspect the algorithm is just the frontloaded questions they ask you -- of course they can shrink all that down into a handful of bytes and unpack it on the other end as "car crash, 3 people, injuries reported, lat/long".

So the percentage "works", in a way, until you get to the freeform text.

Also, a 75% reduction (which I assume was meant by their 300 percent) is not that impressive when it comes to text compression. I'd guess that should be easily reachable with zstd by just creating a pre-shared dictionary generated from a bunch of typical emergency messages. Especially when those messages are partially auto-generated by a wizard-style questionnaire and will thus adhere to a previously-known structure and contain a lot of known elements and words.

You know damn well there's a new "Staff Engineer" at Apple who fluffed this "algorithm" up as an argument for a promotion from Senior Engineer. And likely a few product folks and managers who ballooned this entire project way out of proportion for their own career advancement.

From my friends who work at Apple, there’s a lot less of that promotion-driven work because most of the engineers there are at ict4.

Staff engineer at apple discovers gzip

My guess is 67% reduction.