All other things being equal, (food production, installed PV systems) doing well is a sign that policies are on a good path. The problem is, as soon as you start subsidizing same, things are no longer equal, and the rule no longer applies. To get a quantitative analysis on what I am saying is that the theoretical test that there is a net positive is to calculate the effects of removing the subsidy and seeing if future taxes on the industry can repay the sum cost of the subsidy over the period it operated over. To be fair, one can include taxes intrinsic to the industry during and after the subsidy period.
Quantitatively, to measure the net effect of the subsidy, consider it like an investment, the return on investment being how much extra tax can be extracted from industry for the amount of subsidy spent. It is clear that on this count, that virtually all subsidies ever devised are loss making black holes. It is highly unfair to assume illeffects of taxes on commerce, when the root cause is the black hole of subsidies.