Read it: through the wide-gap years the pair's implied volatility (orange) stays elevated and spike-prone — the gap's footprint really is volatility, not a smooth trend. This looks like an FX story. But that volatility doesn't stay in one currency — so where does it travel next?

Read it: when the dollar broadly strengthens, global financial conditions tend to tighten and hedging pressure builds; when it falls, conditions ease. It is the fastest read on the backdrop the plumbing operates in (not a hedging cost itself — currencies have many drivers). But hold on: the textbook says the rate gap that started all this should simply cancel out in the currency. If it did, none of this would matter. Does it?

Read it: if parity held, the higher-yielding currency should drift down to erase its rate advantage. Over this window it didn't — that persistent, un-cancelled gap is the premium the research measures. (Many things move a currency short term; the point is the systematic average, not any one move.) So the market is clearly pricing a rate risk. How does it price it?

Read it: rate volatility clusters and spikes — this is the 'temperature' the whole market watches. But it is only the level. The research's point is the shape underneath it, which tells you the direction of the risk. Now the payoff: what happens to everything else when this number jumps?

Read it: rate volatility (orange) and the compensation demanded on high-yield bonds (green) rise and fall together — the rate-vol signal lands directly in the price of credit. One gauge, read across the whole chain we just walked.