You posed some fantastic questions, jjharris!
By using your shares to support an advocacy campaign with an individual stock, I think you will marginally increase the success probability of the campaign. I can’t say that you will generate abnormal returns. I did link to a couple studies that correlate successful advocacy campaigns with outperformance, but it’s in no way guaranteed.
Separately (or additionally), investing in a mutual fund/ETF run by an impact-focused investment manager gives it more assets, which gives it more operational capacity to pursue more social good, as well as a more powerful voice in all its advocacy campaigns.
How does impact scale with a greater holding: James Gifford has the seminal work on this topic (https://www.slideshare.net/slideshow/embed_code/key/E28F5ODb5Rk2tu). Gifford finds some correlation between assets and effective engagement. But he makes the critical point that successful shareholder advocacy operates primarily on persuasion, not coercion. Having more assets does increase a shareholder advocate’s credibility, but it’s really about ability to convince management.
Also, Gifford details how smaller investors have been able to raise issues to companies from the shareholder perspective, and build coalitions/generate press coverage to leverage their small stake and still drive impact.
Your question of whether it’s the best investment of your time is another good one, and very difficult to answer. There is not sufficient academic research comparing the effectiveness of advocacy from the shareholder angle to advocacy from traditional nonprofit angles. I think this would be a very worthwhile pursuit, and would love to see this happen. I will say that some nonprofits (animal welfare ones especially) have seen the value of the shareholder angle, and have partnered with investors, or used their own endowments as leverage in the past.
The reason why I wanted to write this piece (my perspective, can’t speak for Max) was to make the point that shareholder advocacy has been historically successful, and that it is not obvious that one that pursues a shareholder advocacy investment strategy (themselves or investing in a shareholder advocacy fund) will lead to financial underperformance. Therefore, shareholder advocacy should not be written off, and is worthy of consideration of serious EA individuals and organizations.