Yield Curve Shifts (Reading 21 - FI Portfolio Mgmt)

In reading 21 Fixed Income Portfolio Management, the CFAI text states that “[yield curve shifts] typically account for about 90 percent of the change in value of a bond” (page 135). The text goes on to state, on the next page, that “parallel shifts in the yield curve are relatively rare” (page 136). These two sentences seem somewhat contradictory. Is the idea that changes in the price of a bond are relatively rare but, when they do occur, they’re 90% attributable to shifts in the yield curve. Please help!

it just means this -> 90% of bond price changes are due to yield curve shift and those yield curve shifts ARE NOT PARALLEL yield curve shifts. They are more oftens twists and what have you. If you think a parallel shift occurs - it does not. So those sentences are not contradictory at all.

Price of a bond does change, most often (90% of the time) due to shifts in the yield curve - most of which are not parallel shifts. --> this is another way of saying all that in the book.

Thanks, cpk123, that’s extremely helpful!