The Securities and Exchange Commission approved a rule Wednesday to require fund companies to enhance disclosure of discounts for which investors are eligible. It would require funds in their prospectus to provide a brief description of arrangements that result in so-called breakpoint discounts, including a summary of eligibility requirements. Breakpoint discounts are volume markdowns applied to the "front-end sales load" charged to buyers of mutual fund shares. Typical breakpoints apply to investments ranging from $25,000 to $1 million.