Or a simple Perl one-liner: 
$ echo '
james     yes
dave      yes
mike      yes
ken       no
jon       yes
jon       no
ken       yes
jon       yes
mike      no
james      yes
dave      yes
mike      no
ken       no
jon       yes
jon       yes
' | perl -nE 'my ($name, $val) = split; $hash{$name} ++ if $val eq "ye
+s"; END{ say "$_\t$hash{$_}" for keys %hash}'
james   2
mike    1
dave    2
jon     4
ken     1

[download]
I realize that you spoke about col5, but I had to use the data as you supplied it. If the flag is really in col5 (i.e. presumably field subscript 4), change the one-liner to: 
perl -nE 'my ($name, $val) = (split)[0,4]; $hash{$name} ++ if $val eq 
+"yes"; END{ say "$_\t$hash{$_}" for keys %hash}'

[download]

In reply to Re: keep only unique elements in an array displaying number of duplicates. by Laurent_R
in thread keep only unique elements in an array displaying number of duplicates. by john.tm

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