The US dollar just had a rough week. The Bloomberg Dollar Spot Index, which tracks the greenback against a basket of 10 major currencies, dropped 1.2% over the past five trading days, landing near the 1,208 level.

Why the BBDXY matters more than you think

The one most people know is the ICE US Dollar Index, or DXY, which measures the buck against six major currencies. The Bloomberg Dollar Spot Index takes a wider view, tracking 10 currencies that represent roughly 81% of US trade and about 93.7% of daily foreign exchange volume.

The BBDXY rebalances annually on the last business day of June, and its broader basket, which includes emerging market currencies like the Brazilian real alongside developed market stalwarts, makes it a more nuanced gauge of dollar strength.

The dollar-Bitcoin inverse relationship

Econometric models using techniques like Fully Modified Ordinary Least Squares (FMOLS) and Dynamic Ordinary Least Squares (DOLS) have found a statistically significant negative relationship between dollar index strength and Bitcoin prices.

Major declines in the dollar index of 5% or greater have historically preceded Bitcoin rallies averaging over 40% within a six-month window since 2020.

Context and caveats

This five-day slide fits within a broader pattern of dollar weakness that has been apparent through mid-2026. Crypto analysts have increasingly made it standard practice to monitor shifts in the BBDXY alongside Federal Reserve policy signals, as prolonged dollar weakness has frequently coincided with bullish phases for Bitcoin and altcoins.

The inverse correlation between the dollar and crypto isn’t ironclad. During broad macroeconomic downturns or risk-off episodes, the relationship can break down entirely.