Any discussion about decline in the US should look to Britain for historical guidance.

Like the US, Britain started from a position of technological leadership and absolute economic preeminence.  As the technologies diffused, it was doomed by its small population to relative decline. Even if it had maintained its leadership in terms of income per capita, its total GDP would inevitably be eclipsed by GDP in US, just at GDP in the US will surely be surpassed by GDP in China.

Britain has, nevertheless, remained a world leader. It has an asset that GDP can’t buy.

Gordon Brown once observed that in establishing the rule of law, the first five centuries are always the hardest. Does this mean that each country follow this same slow path?

Of course not. The Privy Council now acts as the court of appeal for many nations in the Commonwealth. They retain local executive and legislative capacities, even their existing legal traditions. But through this arrangement, younger nations get instant access to a credible form of judicial independence. The new debate in Britain asks whether this arrangement could voluntarily be extended beyond the Commonwealth. See, for example, the discussion about Honduras’ preparation to send appeals to the Privy Council.

This debate has opened up because of efforts in Honduras to develop a new city-scale reform zone. (For more on this strategy, as highlighted in Brandon Fuller’s recent post.) The conjecture is that Britain could encourage in other places the kind of development that it spurred in Asia by fostering an outpost of British law in Hong Kong.

If, indeed, the rule of law is among the most important human inventions, the UK could continue to exert for decades — perhaps forever — an outsized influence on world affairs. All it needs to do is keep encouraging the spread of its most important invention.

Paul Romer is Professor of Economics at New York University’s Stern School of Business and Director of its Urbanization Project. The Urbanization Project addresses a truly historic challenge and opportunity: welcoming an additional 3 – 5 billion people to urban life in less than a century.