Non-parallel rate scenario
Definition
An interest rate scenario in which different points on the yield curve move by different amounts, changing the shape of the curve. Includes steepeners (long rates rise relative to short), flatteners (short rates rise relative to long), and short rate shocks.
What This Actually Means
Rather than the whole curve shifting uniformly, the curve twists or rotates. A steepener widens the spread between short and long rates; a flattener compresses it. These scenarios reflect the more typical behaviour of yield curves during rate cycles — central bank action moves the short end sharply while the long end moves by a different amount, driven by inflation expectations, term premium, and market dynamics. The EBA prescribes two non-parallel scenarios: a short rate shock up and a short rate shock down, which cause the curve to steepen or flatten respectively.
Where It Matters
Non-parallel scenarios are less intuitive than parallel shocks — steepeners and flatteners require management to think about relative movements across different maturity points simultaneously, which is harder to communicate and harder to set risk appetite around. This is precisely why they tend to receive less attention, and why the risks they reveal are more likely to be hidden.
The key diagnostic value of non-parallel scenarios: they detect structural mismatches that parallel shocks cannot see. A bank may show low EVE sensitivity under a parallel shift because its overall duration is broadly matched — but this can mask two equal and opposite risks sitting at different points on the curve, effectively netting each other out in a parallel scenario but both becoming loss-making in a curve reshaping. A steepener exposes one side of this hidden mismatch; a flattener exposes the other. Non-parallel scenarios are therefore not just additional stress tests — they are the tool for uncovering disguised concentrations of risk within an apparently hedged book.