Universal Suffering Units (USU)

1. What is a Universal Suffering Unit (USU)?

A Universal Suffering Unit (USU) is a calibrated measure of experienced suffering. It scales with how intense an experience feels, how long it lasts, and how many people are affected.

Formally, USU aggregates intensity‑over‑time curves on a 0–10 scale, with a modest non‑linearity so that very intense states count more per unit time than mild ones. The unit is anchored so that a typical episode of renal colic (kidney‑stone pain) over its full trajectory is defined as 1.0 USU.

2. How is USU anchored to real experiences?

To keep USU intuitive, we use a small ladder of everyday anchors:

• ≈ 0.001 USU – a brief needle stick for a blood draw.
• ≈ 0.01 USU – a paper cut or stubbed toe.
• ≈ 0.1 USU – a second‑degree burn on a fingertip with a few hours of throbbing.
• 1.0 USU – a typical renal colic (kidney‑stone) episode over its full course.

Other states are placed on the same ladder by panels of people familiar with those states (including, where possible, people with lived experience). The aim is not perfect precision, but a shared, explainable reference scale.

3. How does USU treat very intense versus mild suffering?

USU uses an exponent p (with p ≥ 1) on the intensity scale. When p > 1, holding time constant, very intense experiences contribute more USU than proportionally milder ones.

Intuitively, this reflects the idea that increasing pain from 8/10 to 9/10 is “worse” than increasing from 1/10 to 2/10, even though both changes are +1 on the numeric scale. The exponent is documented and can be changed by other researchers in their own applications if they prefer a different curvature.

4. How would I use USU in my own work or dataset?

The basic recipe is:

• Define the states you care about (e.g., mild dengue, long‑term displacement, moderate depression).
• Assign intensity bands on the 0–10 scale for a typical day in each state, using the anchor ladder (needle, cut, burn, kidney stone) as reference.
• Specify duration patterns (how many days or months, and whether intensity is constant or changes over time).
• Multiply by population – for each state, combine intensity, duration, and the number of people affected.

Templates and example CSV files in the preprint supplement show how to implement this in practice (including Monte‑Carlo uncertainty). USU is designed so other groups can plug in their own assumptions and recompute totals transparently.

5. How does USU relate to WSI and other metrics?

USU is the underlying unit; the World Suffering Index (WSI) is one applied project that uses USU to describe country‑level suffering, alongside simple death counts (and, in future, years of life lost).

USU is intended to sit alongside, not replace, existing measures such as DALYs, QALYs, HDI, or economic indices. DALYs and QALYs track time lived with disability and time lost to early death; USU focuses specifically on experienced suffering (including non‑health harms such as displacement, fear, grief, and some forms of violence).

6. Where can I find a more detailed methods FAQ?

For a longer methods‑focused FAQ that covers both USU and the World Suffering Index (WSI), please see:

World Suffering Index – Methods FAQ

That page goes into more depth on topics such as overlap rules, the USU Catalogue of states, psychological suffering, and how USU is used in country‑level reporting.