From a story I wrote for NZ Business on the evolution of device screen sizes:
…Kantar Worldpanel, another research company, points out, there’s a practical limit to smartphone size. Kantar says phone buyers gravitate to devices in the 4.7 to five inch range. It doesn’t matter how thin and light devices are, anything bigger than five inches can’t realistically fit in a pocket.
Kantar reports that in 2013 the majority of people with phones smaller than 4.4 inches switched to a bigger device when they replaced their smartphone. Most of those who started with larger phones didn’t move up a size.
So there you have it, people have decided the ideal screen is more than 4.4 inches, less than five inches.