You would think policy makers have an obligation to track this, but they don't. There are no studies, KPIs or attempts at tracking effectiveness of subsidy policy.
The burden of proof should be on the policy maker and subsidizer to ensure the purported goals of spending tax many are met.
My wife works in public procurement for research, but there too suggesting such a thing is taboo.
This is of course by design: subsidies are a political tool for passivation of opposition, soft bribery and economic channeling of economic and societal outcomes. The less oversight and transparency the better.
The Flanders region only got a publicly and centralised database of (some) subsidy channels in 2019, after decades of liberal and right-leaning people lobbying for transparency.
There is no such initiative for our federal government.