What does decile mean?
A decile is a statistical measure that divides an ordered set of data into ten equal parts, each containing one tenth of the observations. The boundaries between these parts are also called deciles: the first decile marks the point below which ten percent of the data fall, the fifth decile coincides with the median, and the ninth decile marks the point below which ninety percent fall. In everyday use, the word most often appears when discussing how people, schools, or households compare with others — for example, families 'in the top decile' of earners are among the wealthiest tenth of the population, while pupils 'in the bottom decile' rank near the lowest tenth academically. Derived from Latin roots meaning 'ten,' the term belongs to the same family as decimal and percent, and it serves as a coarser alternative to the percentile, which divides data into one hundred parts. Decile is chiefly found in formal contexts such as government reports, academic research, and economic analysis.
nounAny of the nine values that divide a ranked set of data into ten equal parts, or one of the ten groups so produced; a person or thing falling within such a group.
- One of the nine values dividing a ranked statistical distribution into ten equal parts.
- One of the ten groups of cases produced by such a division, especially as used to describe income or performance rankings.
"Households in the top decile of earners saw their incomes rise fastest over the decade."
"The school's exam results placed it in the top decile nationally."
"Researchers compared vaccination rates across the lowest and highest deciles of household wealth."
The plural is regular; it commonly appears in comparative phrases such as 'across all deciles' or 'the top and bottom deciles.'
"Average spending varied considerably across the income deciles."
If your salary is 'in the top decile,' you're out-earning at least ninety percent of the people you're being compared with — decile literally means 'a tenth.'
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of decile
The word decile derives from the Latin 'decimus,' meaning 'tenth,' combined with the '-ile' suffix used for ordinal-like measures, by analogy with earlier terms such as quartile and percentile. It entered English in the early twentieth century, when statisticians were formalizing vocabulary for describing distributions. It shares its root with other English words from the Latin 'decem' (ten), including decimal, decimate, and December.
How decile is actually used
Decile is primarily a formal, technical term used in statistics, education, economics, and public policy reporting. It typically appears in phrases like 'the top decile' or 'the bottom decile' rather than on its own. It carries no emotional connotation, though references to lower deciles often appear in discussions of poverty and inequality.
Easily confused with decile
A percentile divides data into 100 equal parts, while a decile divides it into only 10.
A quartile splits data into four equal quarters, whereas a decile splits it into ten equal tenths.