Bilateral agreements are intrinsically more difficult to evaluate than either multilateral or unilateral liberalisations because of their second best nature ie the balance of costs and benefits is not a given… This problem of measurement is further complicated because increasingly RTA go beyond the simple dismantling of border barriers to trade in goods…

For administrations in developing countries where human capital is often the binding constraint the resource demands of negotiating one or more RTA alongside multilateral and unilateral trade policy-making are potentially much greater. This is a recipe for misunderstandings about implications of specific policy changes demanded by an agreement and in particular for economic and social development. All of this is further complicated by the possibility that each RTA negotiated by any given country could differ markedly from other RTAs under negotiation or in operation by or in that country.

Jim Rollo – The Challenge of Negotiating RTAs for Developing Countries: What could the WTO do to help? (pdf)