当一个行业的技术无法继续迅速提高时——表现在该行业已不再一定需要绝对现代的机械设备、对高技术工人的需求

下降，以及采用最新技术只能带来微弱优势时——该行业原有的集中分布就会瓦解，生产会转移到低工资的地区。这种情形在现实中相当普遍，试运用外部经济理论解释上述行业集中分布何以趋于瓦解。

It is fairly common for an industrial cluster to break up and for production to move to locations with lower wages when the technology of the industry is no longer rapidly improving--when it is no longer essential to have the absolutely most modern machinery，when the need for highly skilled workers has declined，and when being at the cutting edge of innovation conveys only a small advantage．Explain this tendency of industrial clusters to break up in terms of the theory of external economies．