More on geography's relation with the growth effects of technological gaps

I should clarify and expand my post on Monday on the relation of geography, growth, and technological gaps. When a country has a close trading or geographical relation with another country, then if the countries have similar levels of telephone ownership, the growth of the country with the lowest level is promoted to a greater extent than if the countries have a wider difference of ownership. If the countries are more separated in their relationship, then the lower level country's growth is promoted to a greater extent when the gap is greater. If we look at computer ownership rather than telephone ownership, it is usually only the first case which applies, so a narrow gap is usually better for growth.

I think there are at least three effects in operation:
1. Straightforward technology transfer between countries
2. Clustering effects
3. Terms of trade changes

The first accounts for the positive relations between the gap and growth, the last two account for the negative relations.