Relative Frequencies. Each square represents the approx percentage of all phonemes used in English (both consonants & vowels), rounded to the nearest order of magnitude. Different colours show different vowels. Hence the /i/ vowel in ‘sleep’ is twice as common as the /e/ vowel in ‘slept’; and the /ɩ/ vowel in ‘slip’ is as common as both of them combined. The Schwa vowel /ə/ is the most common as it substitutes for other vowels when unstressed in many varieties of English. Vowels arranged approximately according to height and backness, as in the vowel chart of the International Phonetic Alphabet (IPA). Frequency listing from blogpost by Dan Blumeyer who ‘correlated the Carnegie Mellon University Pronouncing Dictionary with Adam Kilgraff’s unlemmatized frequency list for the British National Corpus.’ Original Data Source: https://cmloegcmluin.wordpress.com/2012/11/10/relative-frequencies-of-english-phonemes