It shouldn't be that hard to track conversion rates?,
You could run A/B tests on randomized populations, to see relative performance of conventional methods to yours, keeping other factors like packaging, contents of the leter same ?
You could even probably track basis demographic/ economic groups given that you are tracking home value, you have both property tax and location data with which to control for.
Ah yeah I guess I shouldn't have said it that way.
I'll rephrase: "It's hard for me, as the individual developer at a company, to spend enough time to devise a system to adequately A/B test the production and distribution of physical mail as compared to link clicks."
You could run A/B tests on randomized populations, to see relative performance of conventional methods to yours, keeping other factors like packaging, contents of the leter same ?
You could even probably track basis demographic/ economic groups given that you are tracking home value, you have both property tax and location data with which to control for.
Whether you should do is a different question