The stock agencies such as Alamy and PD will have thousands of photographers on their books, making it near impossible for them to produce such reports.
Agencies such as Getty etc. have regional headquarters and usually deal in much lower numbers of photographers - usually in the dozens or so - and thus are more able to provide such statistics.
Case in point: the agency that gives me 60% comission has just 20 photographers on their roster. The other has 59 main conrtibutors and and accepts work from stingers too. I can only guess at how many contributors that Alamy has, but it must easily run into the thousands
