Fiat currency and Bitcoin are two competing monetary systems.
The former is dominant in terms of usage, familiarity and volume. For most people, there’s little choice but to use it. Arguably, it is rooted in injustice.
The latter is nascent with a small but committed group of adherents. Participation is currently voluntary which makes its current value all the more remarkable. Arguably, it is more ethical than fiat.
Developments in fiat will inevitably have an impact on Bitcoin so it makes sense to analyse fiat data and extrapolate an impact on the other system.
An overlap, an ebb and flow between the two and cross-references are inevitable until one is completely vanquished.