[Edited to add the second sentence of the paragraph beginning, "Putting these together."]

The primary result doesn't speak to this, but secondary results can shed some light on it. Overall, I'd guess persistence is a touch less for policies with much more support, but note that the effect of proposing a policy on later policy is likely much larger than the effect of passing a policy conditional on its having been proposed.

The first thing to note is that there are really two questions here we might want to ask:

1. What is the effect of passing a policy change, conditional on its having been proposed, when its support is not marginal?
2. What is the effect of proposing a policy change when its support is not marginal?

I'll speak to (1) first. 

The main thing we can do is look at states that require a supermajority to pass a referendum in Appendix Figure E15. This does not directly answer (1) because, while it allows us to look at referendums whose support is well above 50%, it is looking at cases where you need more than 50% to revisit the referendum. Nevertheless, it gives us some information. First, things look similar for the most part. Second, it looks like maybe there's a higher chance that supermajority referendums pass later on, especially in the first decade, though it's very noisy statistically. Third, repeal is slightly less common, though this is again noisy and also confounded with the higher difficulty of repealing one of these.

In the latest version of the paper, I include a simulation (Section 5.1) that allows me to simulate some relevant experiments, though these are currently not in the paper. In my simulation, I can simulate the effect of passing an initiative (a referendum by petition) with varying levels of support. It is generally the case that, for policies that get proposed and have support above 55%, persistence is about 25% smaller at 100 years for the reason you give: these policies are more likely to pass eventually. (I do this by simulating a world where, holding  voter support constant, I randomly assign policies to be passed or not.)

Putting these together, I think it would be reasonable to think either that the effect of passage is similar for policies with widespread support, or that it is somewhat smaller. You can also look at the discussion of state legislation in section 6, which does not rely on close votes (though plausibly selects for things being marginal by focusing on adoptions of policies by states where similar states lack those policies).

Turning to (2), we should expect the effect of proposing a policy on whether that policy is in effect later on to be much larger than the effect of passing a policy conditional on its being proposed. Appendix Figure E20 (formerly D20) is one attempt to get at this and suggests the effect of successfully proposing a policy is ~50% larger than the effect of passing a proposed one. One could also imagine simulating this—but that exercise requires some unclear assumptions, so I'm inclined to go with Appendix Figure E20 here.*

One underlying theme in all of this is that the people who propose policies are very much in the driver's seat. Persistence largely appears to be a result of the fact that small numbers of people can set policies based on whether they decide to pursue policy changes or not.

*One could also imagine simulating this, but the problem there is that the vast majority of policies one could conceive of probably have approximately nobody who cares about them (e.g., minor tweaks to the language of some law, declaring that pistachio is the best ice cream flavor and offering an infinitesimal subsidy for it). My calibration has the policies that get proposed as being in the tail of the distribution in terms of how much people care about them. As a result, if we look at policies that don't get proposed, basically nobody would ever bother trying to repeal or revisit them.

Yep, at the risk of omitting others, Lukas Freund as well.

Yes, it's a good point that benefits and length of the period are not independent, and I agree with the footnote too.

I would note that the factors I mentioned there don't seem like they should change things that much for most issues. I could see using 50-100 years rather than, e.g., 150 years as my results would seem to suggest, but I do think 5-10 years is an order of magnitude off.

Easy Q to answer so doesn't take much time! In economics, the norm is not to publish your job market paper until after the market for various reasons. (That way, you don't take time away from improving the paper, and the department that hires you gets credit.)

We will see before long how it publishes!

1. I look at some things you might find relevant here. I try to measure the scale of the impact of a referendum. I do this two ways. I have just a subjective judgment on a five-point scale, and then I also look at predictions of the referendum's fiscal impact from the secretary of state. Neither one is predictive. I also look at how many people would be directly affected by a referendum and how much news coverage there was before the election cycle. These predict less persistence.
2. This is something I plan to do more, but they can't vary that much because when I look at variables that vary across states (e.g., requirements to get on the ballot), I don't see much of a difference.
3. I'm not totally sure what your question is, but I think you might be interpreting my results as saying that close referendums are especially persistent. I'm only focusing on close referendums because it's a natural experiment—I'm not saying there's something special about them otherwise. I'm just estimating the effect of passing a marginal referendum on whether the policy is in place later on. I can try to think about whether this holds for things that are not close by looking at states with supermajority requirements or by looking at legislation, and it looks like things are similar when they're not as close.

I do look at predictors a bit—though note that it's not about what makes it harder to repeal but rather about what makes a policy change/choice influential decades later.

The main takeaway is there aren't many predictors—the effect is remarkably uniform. I can't look at things around the structure of the law (e.g., integration in a larger bill), but I'd be surprised if something like complexity of language or cross-party support made a difference in what I'm looking at.

Yeah, Jack, I think you're capturing my thinking here (which is an informal point for this audience rather than something formal in the paper). I look at measures of how much people were interested in a policy well before the referendum or how much we should expect them to be interested after the referendum. It looks like both of these predict less persistence. So the thought is that things that generally are less salient when not on the ballot are more persistent.

See my reply to Neil Dullaghan—I think that gives somewhat of a sense here. Some other things:

• I don't have a ton of observations on any one specific policy, so I can't say much about whether some special policy area (e.g., pollution regulation) exhibits a different pattern.
• I look at whether this policy, or a version of it, is in place. This should capture anything that would be a direct and obvious substitute, but there might be looser substitutes that end up passing if you fail to pass an initial policy. The evidence I do have on this suggests it's small, but I still wonder about it.
• My method is about close votes. I try to think about what it means for things that are less close, and I think it basically generalizes, but it gets tricky to think about the impact of, e.g., funding a campaign to move a policy from being unpopular and neglected to popular and on the ballot.

I didn't write down a prior. I think if I had, it would have been less persistence. I think I would have guessed five years was an underestimate. (I think probably many people making that assumption would also have guessed it was an underestimate but were airing on the side of conservatism.)

Yes, basically (if I understand correctly). If you think a policy has impact X for each year it's in place, and you don't discount, then the impact of causing it to pass rather than fail is something on the order of 100 * X. The impact of funding a campaign to pass it is bigger, though, because you presumably don't want to count the possibility that you fund it later as part of the counterfactual (see my note above about Appendix Figure D20).

 Some things to keep in mind:

1. Impacts might change over time (e.g., a policy stops mattering in 50 years even if it's in place). If you think, e.g., transformative AI will upend everything, that might be what you need to think about here in terms of how long this policy change matters.
2. I'm looking at whether this policy or a version of it will be in place. It's possible policies will be substituted for in some way in ways that make things wash out somewhat. (For instance, we don't pass one animal welfare policy, but we pass some policy to shrink the farming sector.) I think this effect is small given the lack of differences by policy topic—this should be much more of an issue for some topics than others—but see the next point.
3. There are some hints of less persistence for policies where there's more room for negotiation/more ways to dial it up and down. See my reply to Erich Grunewald lower down—for taxes and Congressional legislation, it seems like the effect on whether some possibly weaker version of the policy eventually passes might wash out.