In the context of conglomerate merger review, portfolio effects seem to refer to the pro- and anti-competitive effects possibly arising when: the parties enjoy market power but not necessarily dominance; and the products joined are complementary or have analogous properties. When complementary products are merged, there is a potential for considerable synergies that could benefit buyers. There is also an increased potential for forced tying, pure bundling, or analogous practices (e.g. full line forcing) that could restrict buyer choice but also lower prices. Under certain strict conditions, consumers could gain in the short run but suffer long term harm from such practices if they eventually result in a sufficient reduction of competitors and capacity in a market. The hypothetical nature of such harm has led some to conclude that instead of prohibiting mergers having potentially harmful portfolio effects, competition agencies should instead take a wait and see attitude. That would involve using abuse of dominance or monopolisation prohibitions to control negative effects should they actually materialise.