According to Baumol's model of unbalanced growth, if resources are shifting towards industries where productivity is … growing relatively slowly, the aggregate productivity growth rate will slow down. This conclusion is often applied to the … into them may be associated with rising, not falling, aggregate productivity growth …

that these two types of externalities co-exist, but differ in their spatial distribution and attenuation within cities …-city industry cluster in a diversified, large city appears to let firms enjoy the benefits of local industry-specific externalities …