A Moody's Ratings Downgrade for the US: What now?

Aaa no more!

I was on a family vacation in August 2011 when I received an email from a journalist asking me what I thought about the S&P ratings downgrade for the US. Since I stay blissfully unaware of most news stories and things related to markets when I am on the beach, I had to look up what he was talking about, and it was S&P's decision to downgrade the United States, which had always enjoyed AAA, the highest sovereign rating that can be granted to a country, to AA+, reflecting their concerns about both the fiscal challenges faced by the country, with mounting trade and budget deficits, as well as the willingness of its political institutions to flirt with the possibility of default. For more than a decade, S&P remained the outlier, but in 2023, Fitch joined it by also downgrading the US from AAA to AA+, citing the same reasons. That left Moody's, the third of the major sovereign ratings agencies, as the only one that persisted with a Aaa (Moody's equivalent of AAA) for the US, but that changed on May 16, 2025, when it too downgraded the US from Aaa (negative) to Aa1 (stable). Since the ratings downgrade happened after close of trading on a Friday, there was concern that markets would wake up on the following Monday (May 19) to a wave of selling, and while that did not materialize, the rest of the week was a down week for both stocks and US treasury bonds, especially at the longest end of the maturity spectrum. Rather than rehash the arguments about US debt and political dysfunction, which I am sure that you had read elsewhere, I thought I would take this moment to talk about sovereign default risk, how ratings agencies rate sovereigns, the biases and errors in sovereign ratings and their predictive power, and use that discussion as a launching pad to talk about how the US ratings downgrade will affect equity and bond valuations not just in the US, but around the world.

Sovereign Defaults: A History

Through time, governments have often been dependent on debt to finance themselves, some in the local currency and much in a foreign currency. A large proportion of sovereign defaults have occurred with foreign currency sovereign borrowing, as the borrowing country finds itself short of the foreign currency to meet its obligations. However, those defaults, and especially so in recent years, have been supplemented by countries that have chosen to default on local currency borrowings. I use the word "chosen" because most countries have the capacity to avoid default on local currency debt, being able to print money in that currency to pay off debt, but chose not to do so, because they feared the consequences of the inflation that would follow more than the consequences of default:

BoC/BoE Sovereign Default Database

While the number of sovereign defaults has ebbed and flowed over time, there are two points worth making about the data. The first is that, over time, sovereign defaults, especially on foreign currency debt, have shifted from bank debt to sovereign bonds, with three times as many sovereign defaults on bonds than on bank loans in 2023. The second is that local currency defaults are persistent over time, and while less frequent than foreign currency defaults, remain a significant proportion of total defaults.

The consequences of sovereign default have been both economic and political. Besides the obvious implication that lenders to that government lose some or a great deal of what is owed to them, there are other consequences. Researchers who have examined the aftermath of default have come to the following conclusions about the short-term and long-term effects of defaulting on debt:

1. Default has a negative impact on the economy, with real GDP dropping between 0.5% and 2%, but the bulk of the decline is in the first year after the default and seems to be short lived.

2. Default does affect a country’s long-term sovereign rating and borrowing costs. One study of credit ratings in 1995 found that the ratings for countries that had defaulted at least once since 1970 were one to two notches lower than otherwise similar countries that had not defaulted. In the same vein, defaulting countries have borrowing costs that are about 0.5 to 1% higher than countries that have not defaulted. Here again, though, the effects of default dissipate over time.

3. Sovereign default can cause trade retaliation. One study indicates a drop of 8% in bilateral trade after default, with the effects lasting for up to 15 years, and another one that uses industry level data finds that export-oriented industries are particularly hurt by sovereign default.

4. Sovereign default can make banking systems more fragile. A study of 149 countries between 1975 and 2000 indicates that the probability of a banking crisis is 14% in countries that have defaulted, an eleven percentage-point increase over non-defaulting countries.

5. Sovereign default also increases the likelihood of political change. While none of the studies focus on defaults per se, there are several that have examined the after-effects of sharp devaluations, which often accompany default. A study of devaluations between 1971 and 2003 finds a 45% increase in the probability of change in the top leader (prime minister or president) in the country and a 64% increase in the probability of change in the finance executive (minister of finance or head of central bank).

In summary, default is costly, and countries do not (and should not) take the possibility of default lightly. Default is particularly expensive when it leads to banking crises and currency devaluations; the former has a longstanding impact on the capacity of firms to fund their investments whereas the latter create political and institutional instability that lasts for long periods.

Sovereign Ratings: Measures and Process

Since few of us have the resources or the time to dedicate to understanding small and unfamiliar countries, it is no surprise that third parties have stepped into the breach, with their assessments of sovereign default risk. Of these third-party assessors, bond ratings agencies came in with the biggest advantages:

1. They have been assessing default risk in corporations for a hundred years or more and presumably can transfer some of their skills to assessing sovereign risk.

2. Bond investors who are familiar with the ratings measures, from investing in corporate bonds, find it easy to extend their use to assessing sovereign bonds. Thus, a AAA rated country is viewed as close to riskless whereas a C rated country is very risky.

Moody’s, Standard and Poor’s and Fitch’s have been rating corporate bond offerings since the early part of the twentieth century. Moody’s has been rating corporate bonds since 1919 and started rating government bonds in the 1920s, when that market was an active one. By 1929, Moody’s provided ratings for almost fifty central governments. With the Great Depression and the Second World War, investments in government bonds abated and with it, the interest in government bond ratings. In the 1970s, the business picked up again slowly. As recently as the early 1980s, only about thirteen governments, mostly in developed and mature markets, had ratings, with most of them commanding the highest level (Aaa). The decade from 1985 to 1994 added 34 countries to the sovereign rating list, with many of them having speculative or lower ratings and by 2024, Moody's alone was rating 143 countries, covering 75% of all emerging market countries and almost every developed market.

Not only have ratings agencies become more active in adding countries to their ratings list, but they have also expanded their coverage of countries with more default risk/ lower ratings. In fact, the number of Aaa rated countries was the same in 1985, when there were thirteen rated countries, as in 2025, when there were 143 rated countries. In the last two decades, at least five sovereigns, including Japan, the UK, France and now the US, have lost their Aaa ratings. In addition to more countries being rated, the ratings themselves have become richer. Moody’s and S&P now provide two ratings for each country – a local currency rating (for domestic currency debt/ bonds) and a foreign currency rating (for government borrowings in a foreign currency).

In assessing these sovereign ratings, ratings agencies draw on a multitude of data, quantitative and qualitative. Moody's describes its sovereign ratings process in the picture below:

The process is broad enough to cover both political and economic factors, while preserving wiggle room for the ratings agencies to make subjective judgments on default that can lead to different ratings for two countries with similar economic and political profiles. The heat map below provides the sovereign ratings, from Moody's, for all rated countries the start of 2025:

Moody's sovereign ratings

Note that the greyed out countries are unrated, with Russia being the most significant example; the ratings agencies withdrew their rating for Russia in 2022 and not reinstated it yet. There were only a handful of Aaa rated countries, concentrated in North America (United States and Canada), Northern Europe (Germany, Scandinavia), Australia & New Zealand and Singapore (the only Aaa-rated Asian country. In 2025, there have been a eight sovereign ratings changes, four upgrades and four downgrades, with the US downgrade from Aaa to Aa1 as the highest profile change:

With the US downgrade, the list of Aaa-rated countries has become shorter, and as Canada and Germany struggle with budget imbalances, the likelihood is that more companies will drop off the list.

Sovereign Ratings: Performance and Alternatives

If sovereign ratings are designed to measure exposure to default risk, how well do they do? The answer depends on how you evaluate their performance. The ratings agencies provide tables that list defaults by rating that back the proposition that sovereign ratings and default are highly correlated. A Moody's update of default rates by sovereign ratings classes, between 1983 and 2024, yielded the following:

Source: Moody’s

Default rates rise as sovereign ratings decline, with a default rate of 24% for speculative grade sovereign debt (Baa2 and below) as opposed to 1.8% for investment grade (Aaa to Baa1) sovereign debt.

That said, there are aspects of sovereign ratings that should give pause to anyone considering using them as their proxy for sovereign default, they do come with caveats and limitations:

1. Ratings are upward biased: Ratings agencies have been accused by some of being far too optimistic in their assessments of both corporate and sovereign ratings. While the conflict of interest of having issuers pay for the rating is offered as the rationale for the upward bias in corporate ratings, that argument does not hold up when it comes to sovereign ratings, since not only are the revenues small, relative to reputation loss, but a proportion of sovereigns are rated for no fees.

2. There is herd behavior: When one ratings agency lowers or raises a sovereign rating, other ratings agencies seem to follow suit. This herd behavior reduces the value of having three separate ratings agencies, since their assessments of sovereign risk are no longer independent.

3. Too little, too late: To price sovereign bonds (or set interest rates on sovereign loans), investors (banks) need assessments of default risk that are updated and timely. It has long been argued that ratings agencies take too long to change ratings, and that these changes happen too late to protect investors from a crisis.

4. Vicious Cycle: Once a market is in crisis, there is the perception that ratings agencies sometimes overreact and lower ratings too much, thus creating a feedback effect that makes the crisis worse. This is especially true for small countries that are mostly dependent on foreign capital for their funds.

5. Regional biases: There are many, especially in Asia and Latin America, that believe that the ratings agencies are too lax in assessing default risk for North America and Europe, overrating countries in those regions, while being too stringent in their assessments of default in Asia, Latin America and Africa, underrating countries in those regions.

In sum, the evidence suggests that while sovereign ratings are good measures of country default risk, changes in ratings often lag changes on the ground, making them less useful to lenders and investors.

If the key limitation of sovereign ratings is that they are not timely assessors of country default risk, that failure is alleviated by the development of the sovereign CDS market, a market where investors can buy insurance against country default risk by paying an (annualized) price. While that market still has issues in terms of counterparty risk and legal questions about what comprises default, it has expanded in the last two decades, and at the start of 2025, there were about 80 countries with sovereign CDS available on them. The heat map below provides a picture of sovereign (10-year) CDS spreads on January 1, 2025:

As you can see, even at the start of 2025, the market was drawing a distinction between the safest Aaa-rated countries (Scandinavia, Switzerland, Australia and New Zealand), all with sovereign CDS spreads of 0.20% or below, and more risky Aaa-rated countries (US, Germany, Canada). During 2025, the market shocks from tariff and trade wars have had an effect, with sovereign CDS spreads increasing, especially in April. The US, which started 2025 with a sovereign CDS spread of 0.41%, saw a widening of the spread to 0.62% in late April, before dropping back a bit in May, with the Moody's downgrade having almost no effect on the US sovereign CDS spread.

The US Downgrade: Lead-in and Aftermath

With that background on sovereign default and ratings, let's take a look at the story of the moment, which is the Moody's downgrade of the US from Aaa to Aa1. In the weeks since, we have not seen a major upheaval in markets, and the question that we face as investors and analysts is whether anything of consequence has changed as a result of the downgrade.

The Lead-in

As I noted at the start of this post, Moody's was the last of the big three sovereign ratings agencies giving the United States a Aaa rating, with S&P (in 2011) and Fitch (in 2023) having already downgraded the US. In fact, the two reasons that both ratings agencies provided at the time of their downgrades were rising government debt and politically dysfunction were also the reasons that Moody's noted in their downgrade. On the debt front, one of the measures that ratings agencies use to assess a country's financial standing is its debt to GDP ratio, and it is undeniable that this statistic has trended upwards for the United States:

Source: FRED

The ramping up of US debt since 2008 is reflected in total federal debt rising from 80% of GDP in 2008 to more than 120% in 2024. While some of the surge in debt can be attributed to the exigencies caused by crises (the 2008 banking crisis and the 2020 COVID bailouts), the troubling truth is that the debt has outlasted the crises and blaming the crises for the debt levels today is disingenuous.

The problem with the debt-to-GDP measure of sovereign fiscal standing is that it is an imperfect indicator, as can be seen in this list of countries that scored highest and lowest on this measure in 2023:

IMF

Many of the countries with the highest debt to GDP ratios would be classified as safe and some have Aaa ratings, whereas very few of the countries on the lowest debt to GDP list would qualify as safe. Even if it it the high debt to GDP ratio for the US that triggered the Moody's downgrade, the question is why Moody's chose to do this in 2025 rather than a year or two or even a decade ago, and the answer to that lies, I think, in the political component. A sovereign default has both economic and political roots, since a government that is intent on preserving its credit standing will often find ways to pay its debt and avoid default. For decades now, the US has enjoyed special status with markets and institutions (like ratings agencies), built as much on its institutional stability (legal and regulatory) as it was on its economic power. The Moody's downgrade seems to me a signal that those days might be winding down, and that the United States, like the rest of the world, will face more accountability for lack of discipline in its fiscal and monetary policy.

Market Reaction

The ratings downgrade was after close of trading on Friday, May 16, and there was concern about how it would play out in markets, when they opened on Monday, May 19. US equities were actually up on that day, though they lost ground in the subsequent days:

If equity markets were relatively unscathed in the two weeks after the downgrade, what about bond markets, and specially, the US treasury market? After all, an issuer downgrade for any bond is bad news, and rates should be expected to rise to reflect higher default risk:

While rates did go up in the the first few days after the downgrade, the effect was muddled by the passage of a reconciliation bill in the house that potentially could add to the deficit in future years. In fact, by the May 29, 2025, almost all of the downgrade effect had faded, with rates close to where they were at the start of the year.

You may be surprised that markets did not react more negatively to the ratings downgrade, but I am not for three reasons:

1. Lack of surprise effect: While the timing of the Moody's downgrade was unexpected, the downgrade itself was not surprising for two reasons. First, since S&P and Fitch had already downgraded the US, Moody's was the outlier in giving the US a Aaa rating, and it was only a matter of time before it joined the other two agencies. Second, in addition to reporting a sovereign rating, Moody's discloses when it puts a country on a watch for a ratings changes, with positive (negative) indicating the possibility of a ratings upgrade (downgrade). Moody's changed its outlook for the US to negative in November 2023, and while the rating remained unchanged until May 2025, it was clearly considering the downgrade in the months leading up to it.

2. Magnitude of private capital: The immediate effect of a sovereign ratings downgrade is on government borrowing, and while the US does borrow vast amounts, private capital (in the form of equity and debt) is a far bigger source of financing and funding for the economy.

3. Ratings change: The ratings downgrade ws more of a blow to pride than to finances, since the default risk (and default spread) difference between an Aaa rating and a Aa1 rating is small. Austria and Finland, for instance, had Aa1 ratings in May 2025, and their ten-year bonds, denominated in Euros, traded at a spread of about 0.15- 0.20% over the German ten-year Euro bond; Germany had a Aaa rating.

Consequences for valuation and investment analysis

While the immediate economic and financial consequences of a downgrade from Aaa to Aa1 will be small, there are implications for analysts around the world. In particular, analysts will have to take steps when working with US dollars that they may already be taking already when working with most other currencies in estimating basic inputs into financial analysis.

Let's start with the riskfree rate, a basic building block for estimating costs of equity and capital, which are inputs into intrinsic valuation. In principle, the riskfree rate is what you will earn on a guaranteed investment in a currency, and any risk premiums, either for investing in equity (equity risk premium) or in fixed income securities (default spreads), are added to the riskfree rate. It is standard practice in many textbooks and classrooms to use the government bond rate as the risk free rate, but that is built on the presumption that governments cannot default (at least on bonds issued in the local currency). Using a Aaa (AAA) rating as a (lazy) proxy for default-free, that is the rationale we used to justify government bond rates as riskfree rates at the start of 2025, in Australian, Singapore and Canadian dollars, the Euro (Germany). Swiss francs and Danish krone. As we noted in the first section, the assumption that governments don't default is violated in practice, since some countries choose to default on local currency bonds, rather than face up to inflation. If that is the case, the government bond rate is no longer truly a riskfree rate, and getting to a riskfree rate will require netting out a default spread from the government bond rate:

Risk free rate = Government Bond rate − Default spread for the government

The default spread can be estimated either from the sovereign bond rating (with a look up table) or a sovereign CDS spread, and we used that process to get riskfree in rates in a host of currencies, where local currency government bonds had default risk, at the start of 2025:

Thus, to get a riskfree rate in Indian rupees, Brazilian reals or Turkish lira, we start with government bonds in these currencies and net out the default spreads for the countries in question. We do this to ensure that we don't double count country risk by first using the government bond (which includes default risk) as a riskfree rate and then using a larger equity risk premium to allow for the same country risk.

Now that the US is no longer Aaa rated, we have to follow a similar process to get a riskfree rate in US dollars:

• US 10-year treasury bond rate on May 30, 2025 = 4.41%

• Default spread based on Aa1 rating on May 30, 2025 = 0.40%

• Riskfree rate in US dollars on May 30, 2025 = US 10-year treasury rate - Aa1 default spread = 4.41% - 0.40% = 4.01%

This adjustment yields a riskfree rate of 4.01% in US dollars, and it is also built on the presumption that the default spread manifested after the Moody's downgrade on May 16, when the more realistic reading is that US treasury markets have been carrying a default spread embedded in them for years, and that we are not making it explicit.

The ratings downgrade for the US will also affect the equity risk premium computations that I use to estimate the cost of equity for companies. As some of you who track my equity risk premiums by country know, I estimate an equity risk premium for the S&P 500, and at least until the start of this year, I used that as a premium for all mature markets (with a AAA (Aaa) rating as the indicator of maturity). Thus, countries like Canada, Germany, Australia and Singapore were all assigned the same premium as that attributed to the S&P 500. For countries with ratings below Aaa, I added an "extra country risk premium" computed based upon the default spreads that went with the country ratings:

With the ratings downgrade, I will have to modify this process in three ways. The first is that when computing the equity risk premium for the S& P 500, I will have to net out the adjusted riskfree rate in US dollars rather than the US treasury rate, yielding a higher equity risk premium for the US. Second, for Aaa rated countries, to the extent that they are safer than the US will have to be assigned an equity risk premium lower than the US, with the adjustment downward reflecting the Aa1 rating for the US. The third is that for all other countries, the country risk premium will be computed based upon the the their default spreads and the equity risk premium estimated for Aaa rated countries (rather than the US equity risk premium):

How will the cost of equity for a firm with all of its revenues in the United States be affected as a consequence? Let's take three companies, one below-average risk, one average-risk and one above average risk, and compute their costs of equity on May 30, 2025, with and without the downgrade factored in:

As you can see, the expected return on the S&P 500 as of May 30, 2025, reflecting the index level then and the expected cash flows, is 8.64%. Incorporating the effects of the downgrade changes the composition of that expected return, resulting in a lower riskfree rate (4.01% instead of 4.41%) and a higher equity risk premium (4.63% instead of 4.23%). Thus, while the expected return for the average stock remains at 8.64%, the expected return increases slightly for riskier stocks and decreases slightly for safer stocks, but the effects are so small that investors will hardly notice. If there is a lesson for analysts here, it is that the downgrade's effects on the discount rates (costs of equity and capital) are minimal, and that staying with the conventional approach (of using the ten-year US treasury bond rate as the riskfree rate and using that rate to compute the equity risk premium) will continue to work.

Conclusion

The Moody's ratings downgrade of the US made the news, and much was made of it during the weekend that followed. The financial and economic consequences, at least so far, have been inconsequential, with equity and bond markets shrugging off the downgrade, perhaps because the surprise factor was minimal. The downgrade also has had only a minimal impact on costs of equity and capital for US companies, and while that may change, the changes will come from macroeconomic news or from crises. For the most part, analysts should be able to continue to work with the US treasury rate as a riskfree rate and forward-looking equity risk premiums, as they did before the downgrade. With all of that said, though, the Moody's action does carry symbolic weight, another indicator that US exceptionalism, which allowed the US to take economic and fiscal actions that would have brought blowback for other countries, especially in emerging markets, is coming to an end. That is healthy, in the long term, for both the United States and the rest of the world, but it will come with short term pain.

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