Raising the rent in an apartment building

[Maria Wilson]

I own and manage a 33 unit building.  I am planning to raise the rent.  What incentive do you give to have residents sign another 12 month lease instead of switching to month to month?  The last time I raised the rent, it was a 1.5% increase with a 12  month lease and a 3% increase with m2m.  Following that same formula again seems unfair to the ones who already had a 3% increase (3% on top of 3%.)  The 1.5% increase keeps the rate at market value.  Suggestions?