 "At the institutional level, during a transitional period when subscriptions are maintained, the cost of unilaterally adopting Green OA is much lower than the cost of unilaterally adopting Gold OA - with Green OA self-archiving costing average institutions sampled around one-fifth the amount that Gold OA might cost, and as little as one-tenth as much for the most research intensive university. Hence, we conclude that the most affordable and cost-effective means of moving towards OA is through Green OA, which can be adopted unilaterally at the funder, institutional, sectoral and national levels at relatively little cost....In an all-OA world, it seems likely that the net benefits of Gold OA would exceed those of Green OA, although Green OA would have a higher benefit/cost ratio. However, we are not in an all-OA world yet, nor anywhere near it. The most affordable and cost-effective means of moving towards OA in the meantime is through Green OA, which can be adopted unilaterally at the funder, institutional, sectoral and national levels at little cost. Moreover, Green OA may well be the most immediate and cost-effective way to support knowledge transfer and enable innovation across the economy." 