Quintile is a term that comes from the Latin word Quintīlis . According to the dictionary of the Royal Spanish Academy ( RAE ), this is what the fifth month of the year was called in the first Roman calendar .
This calendar was devised in Ancient Rome as a system for dividing time . It was used until the year 46 BC , when Julius Caesar ordered it to be modified and thus the Julian calendar emerged.
In this early Roman calendar, quintile was the fifth month. As the years went by, King Numa Pompilius incorporated two periods, making the quintile the seventh month , being equivalent to July in the Gregorian calendar .
The idea of quintile, nowadays, usually appears in the field of economics . In this case, it is used to classify sectors of the population according to their income .
Thus, the population must be ordered from the poorest subject to the richest. Then you have to divide the population in question into five parts of equal number of members . This allows us to obtain five quintiles , which are ordered according to income level. The first quintile represents the poorest people in society , while the fifth quintile represents the wealthiest inhabitants.
It is important to mention that there are other complementary terms, which allow us to name the concepts that surround the quintile. Just like this one, which serves to represent a distribution in five equal parts, we can also talk about tertile, quartile, sextile, decile and vigintile , depending on whether the distribution is divided into three, four, six, ten or twenty parts, respectively. There are several more, since these are words that are formed with a root that indicates the numerical value and the ending -til .
As a linguistic curiosity, we can focus for a moment on the transition from English to Spanish of this type of word, especially its ending. In English, -tile is generally used (which in some cases is replaced by -cile ), and this leads scientists of our language to hesitate between two possible paths: -til , as we have seen in the previous paragraph, and -linden .
Why use one or the other? Let's start with -til , which is after all the one that completes the quintile term. In the English language we can find several examples of adjectives that end in -tile and in Spanish, in -til , such as the following: contractile, erectile, ductile, infantile, fertile, pulsatile, tactile, retractile and volatile ; All of them derive from Anglo-Saxon constructions that include the letter e at the end. Since quintile in English is spelled quintile , it is understandable that some scientists opt for the version with the -til suffix.
However, since other words that end in -ile in English come to use the suffix -tilo in Spanish (such as acentronitrile, basophile, neuropile and neutrophile ), it is possible to refer to the concept of quintile as quintile . This same extends to the others, mentioned above, so that we obtain tertile, quartile, sextile, decile and vigintile .
Similarly, the notion of quintile is used in statistics when the distribution is divided into five parts . Therefore, a quintile is equivalent to 20% of the total.
Quintil , finally, was the name that the aborigines gave to the valley that is crossed by the San Francisco estuary (or Quilpué ) in the current territory of Chile . The Picunches lived there before the European conquest.
Among the typical activities of the Picunches were sea lion hunting and fishing, which they carried out to later sell their prey to the inhabitants of other valleys .