what is a decile 
a decile is a quantitative method of splitting up a set of ranked data into 10 equally large subsections this type of data ranking is performed as part of many academic and statistical studies in the finance and economics fields the data may be ranked from largest to smallest values or vice versa a decile which has 10 categorical buckets may be contrasted with percentiles that have 100 quartiles that have four or quintiles that have five investopedia danie drankwaterunderstanding a decilein descriptive statistics a decile is used to categorize large data sets from the highest to lowest values or vice versa like the quartile and the percentile a decile is a form of a quantile that divides a set of observations into samples that are easier to analyze and measure while quartiles are three data points that divide an observation into four equal groups or quarters a decile consists of nine data points that divide a data set into 10 equal parts when an analyst or statistician ranks data and then splits them into deciles they do so in an attempt to discover the largest and smallest values by a given metric for example by splitting the entire s p 500 index into deciles 50 firms in each decile using the p e multiple the analyst will discover the companies with the highest and lowest p e valuations in the index a decile is usually used to assign decile ranks to a data set a decile rank arranges the data in order from lowest to highest and is done on a scale of one to 10 where each successive number corresponds to an increase of 10 percentage points in other words there are nine decile points the 1st decile or d1 is the point that has 10 of the observations below it d2 has 20 of the observations below it d3 has 30 of the observations falling below it and so on 