Policy Divergence and the Shifting Baseline of Volatility

[Shadow Trader]

When central banks move in different directions, currency volatility baselines often change with them. Two economies on the same policy path give a pair few reasons to move, since rate differentials stay stable. When paths split, the rate differential becomes a live variable, and every data release gains more weight.

The effect lands on the baseline, not only on event days. Rate expectations are repriced continuously as inflation, employment and central bank communication arrive, so a pair in a divergence phase tends to show wider typical ranges and more frequent directional bursts than the same pair during a synchronised phase. Option markets usually reflect this as higher implied volatility for the affected pairs.

Convergence works in reverse. As policy paths align, a pair that once trended on every data surprise may spend long periods in compressed ranges, and strategies calibrated during the divergence phase may find fewer opportunities and worse spread-to-range ratios.

Practical implications include reviewing volatility baselines when a central bank signals a change in direction, rather than waiting for months of price data to confirm it, and recalibrating average-range assumptions for that pair. Historical ranges from a different policy era may overstate or understate what is normal now. The baseline is a function of policy settings, and policy settings change.