I am thinking, the %age rise in suburban areas is higher than the rest, is it due to the lower $psf + smaller floor area which make it more affordable.
I think this is the group of people who wish to stay in the pte ppty but have budget constraint and this group of people contributes the most.
CCR in my opinion is meant for quite well-off group of people because of its higher $psf + big floor area.
RCR is squeezed in between CCR and OCR, which $psf price is higher than OCR but lower than CCR. RCR is for another group of people where they might also have slight budget constraint but due to its location, they might be willing to foot out slightly more to stay in RCR than OCR.