# How do you quantify the impact on bond if it becomes special?

If the bond is trading at 5% and it becomes special, how do you quantify the impact this has on the bond? Or am I misunderstanding the concept of specialness?

On this day, this issue's 3-month repo rate was 3.14%, so the 3-month forward price is simply: $$99.062 \times \left(1 + 3.14\% \times \frac{89}{360}\right) - 1.230 = 98.602,$$ where 1.230 was the accrued interest as of the forward settlement date.
The general collateral repo rate on the same day was over 200 bp higher at 5.19%. If the bond weren't trading special and had to be financed at GC, the forward price calculated above would imply a spot price as follows: $$P \times \left(1 + 5.19\% \times \frac{89}{360}\right) - 1.230 = 98.602.$$ So without repo advantage, the bond's price should be $P = 98.567$, or a yield of 5.18%. This is 6 bp higher than the quoted yield of 5.12%, indicating that specialness richened the bond by 6 bp.