According to Stevens (1946) ratio level variables require an absolute zero. The implication, I believe, is that 0 = an absence of the thing being measured.

As such, can ratio level scales have negative measurements? We can manipulate the measurements mathematically to get negative numbers, but can we have actual negative measurements?

An internet search results in competing arguments, and I cannot find a peer-reviewed academic work that provides an answer.

Against negative numbers: http://www.statisticshowto.com/ratio-scale/ https://www.dummies.com/education/science/biology/levels-of-measurement-for-biostatistics-data/

For negative numbers (they all seem to use bank balances): http://web.pdx.edu/~newsomj/pa551/lecture1.htm https://www.spss-tutorials.com/measurement-levels/