The July 13 editorial “Bonus levels” speculated that proposed new zoning rules in Montgomery County would not significantly change developers’ incentives to build affordable housing.

What do the data show? How many moderately priced units are developers providing in places such as Bethesda, under older zoning rules, compared with White Flint, where the new zoning was adopted several years ago?

Many Bethesda developers devote 15 percent of their units to affordable housing in exchange for a density bonus, which allows the developers to build and sell larger buildings. White Flint developers have provided no moderately priced housing above the 12.5 percent required by law. They manage to reach their “highest possible density level” without providing any extra affordable housing. The editorial is technically correct; developers do “build affordable housing.” All developers must comply with the county’s enlightened law.

The editorial reflects the confusing mosaic of claims about the new rules. Arithmetic, however, gives a clear answer: The new rules would provide cheaper, simpler ways for a developer to reach maximum density than by making more affordable housing available. Developers can do arithmetic. The Montgomery County Council is still tweaking the rules. Stay tuned.

Pamela Lindstrom, Gaithersburg

The writer is a member of the Montgomery County Housing Opportunities Commission. The views expressed are her own.