"a one off factor" is correct and can be used in written English.
You can use this phrase when you are referring to a single, unique variable or element that is not related to any other elements or variables. For example, "The sudden influx of new customers was a one off factor that caused sales to spike."
She asked Treasury minister Danny Alexander if that should not have been excluded as a one-off factor but was told that there were one-off sales included in the figures every year.
In that sense, it is thanks to another one-off factor.
Ladbrokes sank to a £43.2m loss before tax in 2015, compared with a £38m profit the previous year, after taking into account a range of one-off factors.
Gardner said monthly price changes had been influenced by a number of one-off factors in 2012, such as the end of the stamp duty holiday for first-time buyers: "These are factors that cannot be controlled by the usual process of seasonal adjustment".
It will probably be revised away, and in any case it's the result of one-off factors: a drop in inventories and a quirky sharp decline in defense spending.
Speaking on RTL Radio, Moscovici blamed one-off factors such as slowing aircraft orders (the Paris Air Show, in June, typically delivers a boost to industry), saying: The productive forces are starting up again, production is recovering We knew the third quarter would mark a pause, it's not a surprise, it's not an indicator of decline, it's not a recession.
And if the third quarter is just to be a break between periods of contraction, boosted by one-off factors, then it looks more like a blip in a period of stagnation than a turning point for the economy.
By contrast, the Opposition claims this is an artificial strength due to one-off factors,.
A spokesman for the Treasury said: "One-off factors affected borrowing this month, but it is clear from the downward revision to last year's borrowing figures that the government's deficit reduction strategy is making headway in dealing with our unsustainable deficit".
As this article argues, the overcapacity has come about as a result of two things: recession (which has pushed down industrial demand for carbon, even though the volume of carbon allowances is fixed for 2013-20) and one-off factors such as an increase in the number of carbon auctions.
The deficit figures are harder to analyse because of the one-off factors (Royal Mail pension fund, the 'profits' on quantitative easing, etc), but they show that Britain faces a longer struggle to really get the debt 'under control'.
