Vowels 9 and 12, /u/ versus /ə/ 15 pairs [cuckoo.html]
Since the schwa has to be unstressed while /u/ is likely to be prominent, very few pairs were found in the dictionary. I have included several involving the weak formsbut, cos, from, to, was and you which are of doubtful status since they cannot occur in isolation.
The density figure is 0.32%. The set makes 11 semantic contrasts for a loading of 73%.