There is one big question in Asia. Your hear it in Tokyo, Beijing, New Delhi, Seoul and most points in between. President Barack Obama’s so-called pivot to Asia is all well and good, but beyond the near horizon does the US have real staying power? No one has a definitive answer. But this scarcely deters the speculation.

In the absence of certainty, perceptions count for as much as hard evidence. Some calculation as to how long America is likely to stick around as a resident Pacific power shapes behaviour in just about every capital in the region. Nowhere is the likely trajectory of US power over coming decades more vigorously debated than in Beijing.

China is testing how fast and how far it can push outwards; Japan wants to know whether it can depend on Washington when it pushes back; South Korea, Vietnam, the Philippines and others must choose between balancing or bandwagoning on Chinese power; India is rediscovering long-neglected east Asian ties. To complicate things, the answer to the staying-power question changes with the seasons.