Well, according to
this one source, SCEI's "business development" figures, software sales are aggregated across all games (etc.) which makes sense. So it's down to the developers to share their own figures, if they know them, I guess - to what end, though, when you're first party?
Notice that the PS4 is barely featured, and the most recent software sales figures are for all platforms - more evidence of the future direction Sony is going with its hardware ecosystem, i.e. PSN. But the fact stands, what need do we as gamers have of sales figures, except to fuel debate? They're only an approximate indication of whether we'll get a sequel or not, especially when you factor in time, nostalgia and "re-boots" into the equation.
But this is meandering off-topic.