We entered this negotiation at a time when there were significant differences between countries. (dotearth.blogs.nytimes.com)
In making our estimates, we take into account differences between countries in their level of income, the average number of years students are in school, and population growth rates. (educationnext.org)
But there are stark differences between the countries, blocking any substantive international agreement so far. (ase.tufts.edu)