Comment by didibus

I think you're asking a good question and it's not unreasonable at all.

The way I see it, the private sector is in a place to even potentially be able to fund research because of prior publicly funded research.

The capital expenditure needed to fund research in a way that leads to breakthroughs is massive. Private sector doesn't always have the cash needed. Definitely this was true for a long time, and is true for many countries still.

Then generally the private sector is pretty risk adverse, the majority of private sector funds are retirement and savings. People don't want to risk that, so it tends to invest in short term or more known ventures, which is rarely research.

Some private funding is research moonshots, but the pool of private money interested in that is a lot smaller.

That means, at least historically, private funding simply isn't incentivized to properly fund research, and may not always have the means to do so.

Now should the public still fund it? What kind of ROI does society gets?

Again, at least historically, the ROI has been massive. Let's just look at a short list:

- Internet - GPS - Semiconductor - MRI/CT scans - Vaccines - Jet engine, aviation - Lithium Ion batteries - Touchscreens - AI - Fracking - Mass agriculture - Space exploration

You could also question investment in art and humanities. Private sector simply isn't interested. Do we want to learn about our history, preserve our arts, these don't have financial ROI, but depending on your opinion on the matter they could be societal ROI because you might want to live in a society with a rich culture and record of its heritage and a good understanding of its evolutionary roots and what not.

To be honest, it's hard to find a single private sector breakthrough that wasn't off the back of the public sector either through direct funding, prior discovery or indirect subsidy.

I feel the issue is that after the public funding achieves breakthrough, the private sector quickly capitalizes on the profits. At the same time, the private sector is really good at commercializing and finding efficiency and market fit. The ROI happens indirectly, society modernizes through access to new things, the private sector creates jobs, taxes are paid on private transactions and income generated from the discovery, etc.

At the end of the day, it's all opportunity cost. What else do we do with the money. You said paying down the dept, what's the societal ROI of that? Why not lay down the dept with some of the other tax money? Etc. It's a complex question.