The massive widening of the EMS bands to 15% on either side of a central parity initially made a single currency appear more remote. But it also took away the one-way-bet character of speculative attacks on vulnerable currencies, and thus removed the fundamental driver of instability.
布鲁塞尔的深夜谈判最初拿出的方案看起来有害无益。把EMS波动区间大幅扩大至中间价上下的15%，乍一看只会让单个货币更加孤立。但这一举措也消除了单边下注的条件，令投机性攻击无处发力，从而消解了不确定性的动力。