Ground the selection of PPPs in value for money. This means carefully investigating which investment method is likely to yield the most value for money. It may mean developing a relative VfM test (public sector comparator) that measures the cost efficiency of using a PPP versus using traditional capital procurement. A public sector comparator compares the net present cost of bids for the PPP project against the most efficient form of delivery according to a traditionally procured public-sector reference project. The comparator takes into account both the risks that are transferable to a probable private party and those risks that will be retained by government.