# SABR Question: Why does the market take the beta parameter as a constant?

SABR Question

Why does the market take the $$\beta$$ parameter as a "constant"?

• I see most brokers quoting SABR parameters nowadays.
• I've seen many banks use $$\beta$$=0.5 as a rule.
• I've seen quants select a $$\beta$$ based on best fit to calibration instruments.

What is most correct to the spirit of the paper, and explain any issues to anticipate with IMR/IPV processes.