some small amount of supply can be immediately affected by removing rent control. Take a basement apartment for example. If the market value would be $2,000 per month but government puts a ceiling at $1,000 you might decide it is not worth the headache of renting it out. But if the rent control is abolished you might put it on the market for $2,000. And the long term effects are much more drastic as removing rent control can incentivize development.