LOC is a terrible measure for productivity, but I like to think about it more as a measure of capacity. LOC/day is useful as an upper bound in the same way pages per day is an upper bound for authors. Stephen King is notorious for being one of the most prolific writers, and he can’t produce more than 8 publishable pages a day (top hit on google suggests his average may be close to 6). Knowing that the number of LOC/day is so low on average, can really help keep estimates honest, and remind us how truly difficult what we do actually is.
Isaac Asimov, another prolific author, averaged something like 2800 words per day[1] over the most productive period of his career, which works out to about 9 pages, so that seems like a good estimate.
1: Google is giving a much higher number but they all seem to go back to the same estimate which is more hand-wavy than a printed source I found in college when researching it. Sorry I don't have it to source. The other number from that source was 1800 published words per day if you start from his first published book, which is absurd, since new authors tend to be much less prolific.
Interesting, I'd never thought to look much at other authors output on this topic. There was a post the other day talking about Jules Verne's corpus, and I now wonder what his output was like.
I've another thought on the topic as well, which is that I have a friend who hired a lot of former newspaper journalists circa 08 when there were mass layoffs in that industry. He said they were able to most consistently churn out content for his book over other writers, but that it was significantly lower quality, and needed a lot more rework and polish. For him the tradeoff was worth it, and he organized his time and resources around this increased quantity. But this adds to the idea that you really can't look at pages/day (or LOC/day) on an individual basis either, since it's the whole pipeline that matters. And if you really want to improve total output, you need to look at variables outside of individual contributors. Things like code reviews and QA can perhaps greatly increase total output.
LOC is a poor way to measure progress, but it's not a bad sanity check on time estimates for a proposed project. Most experienced programmers have some points of reference where they know the approximate LOC count, and can make a rough functionality/complexity analogy to a proposal. If the proposal is less time than the team could possibly generate a comparable amount of tested code at 10-100 lines/day (wherever your team is in that range), then you should probably revisit the estimate.
Apply a few of these kinds of comparisons using different metrics, and you may be able to improve your estimates.
"Measuring programming progress by lines of code is like measuring aircraft building progress by weight."
I'm no expert in aircraft, but I'm guessing that in both cases the relationship between progress and the metric in question is logarithmic: The first bits to be put place represent the bulk of the (weight|LOC), but only a relatively small percentage of overall time and effort.
