Perpetual Dickensian Poverty?

This feels like a nice crisp example of how Twitter is broken in ways that generate disinformation. A user with 531 followers, not someone who can reasonably be expected to treat their tweets as a journalistic product or employ a factchecker, made an understandable mistake. This produced a politically-potent but inaccurate soundbite.

A substantial fraction of the quote-tweets are refutations. These are only visible if you check for them explicitly. This creates a confirmation bias trap: if you think the economic left is pushing a false narrative, you'll be more likely to check, see that the tweet is wrong, and reinforce that belief. And if you think that inequality is a huge problem and the economic situation of the poor is dire, then you'll be less likely to check, again reinforcing that belief.

This is specifically a property of systems that don't have downvotes and of systems that don't have a good way of sorting replies, which is why this sort of thing is especially common and especially bad on Twitter..

Yes. And in addition purchasing power doesn't really capture the fact that £1 in 1843 can only be exchanged for the goods and services of 1843. For example 

https://www.statista.com/chart/10567/the-cost-of-light-through-the-ages/

So is comparison at all sensible? Inflation calculations use a basket of goods, but when superior goods are substituted (e.g. light bulbs for candles) the comparison becomes less valid. Over 178 years, the accumulation of substitutions makes quantitative purchasing power comparisons much less meaningful.

I agree that purchasing power is a better way of measuring absolute poverty!

Interestingly, I could imagine the author of the Tweet being right about using labor value, if what they intended to point at is inequality.

Also very misleading to compare to a legal minimum, rather than to a median or comparable book-keeper's wage.  

I expect you'll also get different answers depending whether you convert GBP to USD in 1843 or in 2021. The exchange rates will be different across times and the inflation indexes will be different across currencies.

(Or will those cancel each other out? I wouldn't be shocked, and I haven't looked. But my intuitive guess is something like: "no, not reliably. Maybe if American and British societies look sufficiently similar at both endpoints. Maybe even, only if they follow sufficiently similar trajectories. I wouldn't expect either of those to hold.")

Which is more "correct"? I don't immediately see a reason to think either one is, or indeed that one or the other must be.

Not sure how to gain insight by making such a comparison in the first place, twitter is... I agree that using the cost of labor is not the best way to calculate; however, there is an issue with the calculation of poverty for the period prior to 1981.

This paper finds that the $1.90/day (PPP) line is lower than the level of consumption of enslaved people in the United States in the 19th century.  
 

Likely, the issue here is that inflation calculations use a basket of goods that are substituted over time. Comparisons over time are not the best because a basket of goods from 2021 might include an iPhone, while a basket of goods from 1850 might include a pound of hay... 

That all being said, possibly using a harmonious pricing index might be more fruitful for this discussion. I believe that the UK and Canada use the HPI over CPI, mainly due to the issue of substitutes and compliments over time.

I don't think you are correct. Just using raw absolute poverty isn't a measure that a supporter of government social investment and economic equality would accept.

When you say "what we care about" the we might work in the context of libertarians/classical liberals who may or may not read Lesswrong . com but that we wouldn't include the original tweeter or the people amplifying the tweet.