Beloved by WPP boss Sir Martin Sorrell and many others in the business world, swans in various hues are employed as metaphors for forecasting the future.
A black swan event is completely unpredictable and totally out of the blue. But a grey swan, on the other hand, is more foreseeable.
And Japanese bank Nomura has made its annual forecast for potential grey swans for 2018. We've chosen four of our favourites of its 10 predictions.
"These are the unlikely but impactful events that, in our opinion, lie outside the usual base case and risk scenarios of the analyst community," it said.
Should it be classed as a currency, commodity or asset? Will it boom or bust in 2018? Forget about that, it's so 2017. What may come to the fore in 2018 is the other markets it might have a impact on. Coal for instance.
With bitcoin mining set to consume the same energy as Denmark by 2020 and 71 per cent of bitcoin mining taking place in China where coal powered electricity is cheap, "perhaps the grey swan of next year is not bitcoin’s bubble bursting, as so many commentators tend to suggest, but instead its continued rise and a surging demand for coal," the bank notes.
2. United States of Europe
Ready to pledge your allegiance? Former European Parliament president Martin Schulz has just made noises about it and Nomura identifies three prime reasons why 2018 might just be the right time for such a union to form.
Country level politics will not overshadow things with elections and votes in Germany, France and Catalonia now out the way, and the fallout from which due to be wrapped up early in the year, "not only does this free up bandwidth for key European political actors to think about European matters, but may also end the de facto ban on any European treaty change that has been in place in recent years".
Of course Brexit, which could crystallise the relationships of other countries with the EU as well as a strong European economy "suggests there is no better time to undertake this project than now",
"Something like a United States of Europe cannot be built in a year. But steps on a path that the market understands to be leading there can be taken. A grey swan event for 2018 is that European politicians understand the temporal opportunity they have been given, and undertaking such a path starting with a treaty change that leads to increased mutualisation of debts and sharing of risks. It is important to note that comments from key European leaders are heading in this direction"
3. Middle East
Long simmering tensions may erupt and threaten the region's stability, with risks of escalations in Yemen. and between Lebanon and Palestine, the bank said.
That could have a knock on effect on Credit Defauklt Swap (CDS) spreads and currencies in the countries involved, but more widely, on oil prices and global inflation.
"It is difficult to forecast where oil prices will settle in such a scenario, but we stress-tested our baseline forecasts with the Brent oil price at $80, an increase of around 30 per cent from its current price level," it said.
"With all the usual caveats that apply to such simulations, we find that an oil price shock of this magnitude would add 0.4 and 0.9 percentage points to 2018 headline inflation in the US and eurozone, respectively."
4. Helicopter money
Interest has died down recently after a spike in interest - just look at this Google Trends chart. But Nomura identifies that this could reemerge in 2018 with the Bank of Japan one of the most likely candidates. The bank also noted positive noises for the measure from former Fed chair Ben Bernanke this year.
"We should remember another major central bank, the ECB, also faces limited policy options for resolving negative shocks," it added.