Why Are Nuclear Agreements Credible?

Compliance is a central issue in arms control negotiations. Take Iran as an example. The United States has long pitched a better world standing for Iran in exchange for Tehran ending its pursuit of nuclear weapons. President Obama once described such an agreement in the following way:

Iran must comply with UN Security Council resolutions and make clear it is willing to meet its responsibilities as a member of the community of nations. We have offered IRan a clear path toward greater international integration if it lives up to its obligations…. But the Iranian government must now demonstrate through deeds its peaceful intentions…

At first pass, such a trade may seem impossible. The United States has to give concessions to Iran to make nonproliferation look attractive. But nothing stops Iran from accepting those concessions, building nuclear weapons anyway, and then leveraging its atomic threat for all of the corresponding benefits. Worse, if the United States expects this, then it has no incentive to offer any sort of deal in the first place.

I, for one, certainly felt that way when I watched Obama pitched the deal in 2009. In fact, I wrote a book that explores those incentives, which just came out:

Bargaining over the Bomb’s central finding is that, despite appearances to the contrary, those deals work. Countries like Iran do not have an inherent incentive to take those concessions and run with them. This is true even if Iran could build nuclear weapons without the United States noticing until the bombs are finished.

A little bit of formalization helps explain why. All we need are a few parameters to map out the incentives. Suppose that nuclear weapons are useful for coercive leverage, and let p be the percentage of the benefits the would-be proliferator can extract once it has acquired those weapons. Let c > 0 represent the cost of building them. Finally, let ๐›ฟ > 0 represent how much the would-be proliferator cares about the future.

From this, we can calculate what portion of the benefits the would-be proliferator requires now and for the rest of time to not want to develop nuclear weapons. Let x be that necessary share, so that if a deal is made and sustained, the would-be proliferator receives x for today and ๐›ฟx for the future, for a total payoff of (1 + ๐›ฟ)x.

The apparent barrier to agreements is that the would-be proliferator can take x for today, pay the cost c, acquire nuclear weapons, and then capture p portion of the benefits in the future. And if it can get away with keeping that x value in the interim, why wouldn’t it?

Well, summing up that payoff for proliferation and comparing it to the payoff for accepting the deal, the potential proliferator prefers to not build if:

(1 + ๐›ฟ)x > x + ๐›ฟp – k
x > p – k/๐›ฟ

In fact, the would-be proliferator is willing to accept an agreement after all!

Where did intuition fail us? The key to understanding why an agreement works is that proliferation only provides a finite amount of benefits. If the opponent offers the potential proliferator those benefits up front, then proliferating at that point is unprofitable—developing weapons leaves the potential proliferator exactly where it was before, but it must pay the costs of proliferation in the interim.

We can see those incentives in the minimum acceptable offer. The value x must be close to p—in other words, the quantity of concessions given immediately must be close to the benefits the potential proliferator would receive if it built the weapons.

To be more precise, the opposing state can fudge this a little—by k/๐›ฟ, to be exact. This is because, by accepting the deal, the would-be proliferator does not have to pay the cost to build. Note that when the would-be proliferator does not care at all about the future, ๐›ฟ goes toward 0, and thus the potential proliferator needs less to accept an agreement.

In Bargaining over the Bomb, I develop this model in much greater depth, providing context in how the states calculate the benefits of proliferation, how preventive war fits into this, and whether the opponent would actually want to offer such a deal. But the central finding remains: would-be proliferators are happy to accept agreements. The first half of the book explores some facets of those agreements while the second half explains why bargaining may still fail.

Building this model and writing the book has made me a lot more optimistic about whether negotiations with countries like Iran can succeed. If you share the same skepticism I once did, I would encourage you to read the book and think more about the central incentives at play. I don’t think agreements are universally workable, but they should be a critical part of our policymakers’ tool kits.

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