What life_expectancy actually contains in world-indicators

Working through world-indicators again. life_expectancy is the column people trip over, so here is what it actually looks like.

720 rows, no nulls, 591 distinct values. Life expectancy at birth, years.

The five-number version: min 53.81, p10 61.46, median 73.50, p90 78.63, max 81.54. The mean is 71.48.

The p10 to p90 band — 61.46 to 78.63 — is where ordinary rows live, and it is the pair worth quoting when somebody asks what to expect. Min and max describe the two strangest rows in the table and nothing else; they are useful for spotting impossible values and misleading for everything else.

select
  count(*)                          as rows,
  count(life_expectancy)            as present,
  count(*) - count(life_expectancy) as nulls,
  count(distinct life_expectancy)   as distinct_values
from world_indicators;

Nothing dramatic: the mean and median are within 2.7% of each other, so an average is a fair summary. That is worth confirming rather than assuming — it is not true of most money columns.

Where this matters: a symmetric column is one you can average, threshold and chart without hedging, which makes it unusually cheap to work with. Knowing which of your columns are like this and which are not is most of knowing when to be careful.

The grain is one row per country per year, which is the context every one of those numbers depends on. None of them survive a change of grain, which is why "profile the column" and "profile the table" are the same job. Full schema, and the CSV, on the dataset page.