Sweden's decision to reject the euro may be reciprocated by increasedsuspicion from the members of the single currency, writes KatinkaBarysch.
Swedish voters have rejected the euro by a clear majority. Göran Persson, Sweden's pro-European Premier, said the referendum result reflected "a deep scepticism towards the entire euro project". Some observers have gone further, interpreting it as a no confidence vote in the European Union.
The suspicion could become mutual. In the future, the other EU countries will be less willing to accommodate euro waverers. Sweden's No to the euro will reinforce the trend towards variable geometry (or reinforced co-operation, as it is called in Brussels speak) in the EU.
It is difficult to blame the Swedes for their decision. The eurozone does indeed look fairly uninviting these days. Economic growth is sluggish and jobless queues are getting longer, although this has more to do with inflexible labour markets and other structural flaws than with the euro.
Meanwhile, euro members squabble about whether they are allowed to spend their way out of trouble in defiance of the Stability and Growth Pact.
At the moment, Sweden appears to be doing just fine with its own currency. The Swedish leadership did not make it clear enough that joining the euro would be good for growth, investment and jobs in the medium to long term.
The referendum result will be carefully evaluated in Britain and Denmark, the other two countries that have not yet made up their mind about the euro. The Blair government now looks less likely to call a referendum on the euro during the current parliament (although the delay may have more to do with the government's troubles over the Hutton inquiry than the Swedish euro decisions).
Even in Denmark, where there is now a solid majority in favour of the single currency, the government will think twice before calling another referendum. The last one, in 2000, ended in a clear No to the euro.
Just like after Britain's June decision not to call a euro referendum, Brussels and the other European capitals reacted to the Swedish result with polite sympathy.
"We respect your decision but still hope that you will join us soon," goes the official response. But behind the scenes, euro members are sometimes striking a different note: "If you decide to stay outside, don't expect to be treated like one of us", they grumble.
Already, Sweden and the other reluctant Europeans are losing respect and influence in the EU. They are regarded as less trustworthy. They are accused of free-riding; they let other Europeans take the risk while they are waiting to see if the European project works.
Sweden, Denmark and the UK may now decide to postpone their euro referendums for years to come. The eurozone would then be ringed by a small group of indecisive "outs" as well as a much larger group of keen "pre-ins" after next year's round of EU enlargement.
The Union is not used to accommodating such diversity. But it is waking up to the fact that with 25 members and growing economic and political diversity, it will no longer be able to move in unison. Some members may want to charge ahead - be it in economic integration, foreign policy or internal security - while others will want to take it slowly.
Variable geometry (or reinforced co-operation, as it is also called) has troubling implications for both sides. Euro-enthusiasts dislike it because it goes against the Union's core principles of consensus and solidarity. And Euro-sceptics fear that they could be permanently left out of an ever-tighter and more exclusive club. This is why the EU has so far made sparing use of reinforced co-operation, although the EU treaty already allows it in principle.
This will change, however. The Swedish No will reverberate in the Inter-Governmental Conference that convenes in October to thrash out the details of the new EU constitution.
There will be less patience with, and understanding for, reluctant Europeans. In economic policy-making in particular, the "outs" will no longer have a say in matters that concern the euro, such as the Stability and Growth Pact or exchange rate policy.
The EU's draft constitution already foresees a much stronger role for the Euro Group, the currently informal meeting of eurozone finance ministers. The political costs of staying outside the euro will then be much more tangible.
Katinka Barysch is chief economist at the Centre for European Reform, a London-based EU think-tank