"the only people that said" 28The Longman Grammar of Spoken and Written English analyzes the same issue based on its corpus and finds the same general result, though with greater nuance:
"the only people who said" 115
"the only person that said" 79
"the only person who said" 393
"the first person that came" 691
"the first person who came" 864
"and no man that" 382
"and no man who" 834
"all of the women that" 702
"all of the women who" 2180
[I]n the written registers, there is a very strong tendency for a relative clause with a human head noun to use who rather than which or that.... [R]elative clauses with that freely occur with animate heads, especially in conversation. In fact, for many head nouns referring to humans, that is almost as common as who in conversation. (pp. 612-614)Longman also includes tables of percentages for several patterns.
(May 25, 2003)