Two points are needed to draw the trend line, and a third point to make it valid trend line. Trend lines are used in many ways by traders.

Bollinger Bands adjust themselves to market conditions. When the markets become more volatile, the bands widen (move further away from the average), and during less volatile periods, the bands contract (move closer to the average).

The dollar gained a premium position in The Bretton-Woods Agreement as a reference currency, reflecting the shift in global economic dominance from Europe to the USA.