Answer:
A wider corridor does not mean that different action would need to be taken if a breach beyond 3% were observed. For example, a breach of 4% would still require the same changes in benefits under either a 2% or 3% corridor, because after a breach the aim is to return costs back to target.
However, a 3% corridor will mean that cost changes between 2 and 3% will not trigger a breach and require rectification, which could lead to a larger than otherwise breach occurring at subsequent valuations. The Government considers that, although this risk exists, a wider corridor is necessary to ensure a more stable mechanism and limit the frequency of member benefit and contributions changes.
Furthermore, if a scheme shows cost changes between 2-3% at one valuation, then that does not automatically mean costs would either stay at that level or move further in the same direction at subsequent valuations and therefore result in a breach that would be larger than under a smaller corridor. It is perfectly possible that a scheme may see an increase in costs at one valuation, and then a reduction in costs at the next.