#country Highly skilled foreigners can be useful. -- The flow of brains across borders becomes an ever more important way for new ideas to spread. Most rich countries claim to be eager to attract top talent, yet other priorities often intrude. A smart system for attracting talent should observe two principles: 1. Removing obstacles is more effective than offering inducements. 2. The criteria for deciding whom to admit should be as simple and objective as possible. Those that fail to roll out a better welcome mat will squander a chance to speed the spread of knowledge and make themselves more prosperous.