McKenzie/Ozler et al
In the UK I count
1. The bandwagon effect - Mankiw and Krugman are really high profile and have been blogging for years - when the leading textbook author and a Nobel prize winner are blogging then its probably ok (although this bandwagon effect could also effect UK academics)
2. Differences in administrative/teaching burdens?
3. A selection effect - in the UK terminal masters programmes are more common, so natural writers quit before then complete a phd and get sucked into academia
4. A simple quantity effect - some fixed % of academics are likely to be interested in blogging, and there are just many more top economists in the US than the UK (about 6 times more according to this list).
What am I missing?