Do credit ratings (by Moody's, S&P, and Fitch) have any relevance?
They've pretty much shot any credibility they possessed. Follow the money. "The problems with ratings and the interpretation of ratings is that they are retrospective, and most people read them as prospective. They basically tell you that debtor is solvent right now. What does that mean? It means that the ratings are based on the audited financial statements of a company, government or other organization issuing debt. So, in the best case scenario where the rating agency is acting properly, they are still dependent on folks with fiduciary responsibility telling the truth. And even if they are telling the ""truth"", accounting rules make it possible to obscure problems for years in some cases. Municipal goverments are a great example of this... the general obligation bonds cities and even states with deep structural budget problems still get good ratings, because they are solvent and have sufficient operating cash to meet obligations today. But towards the end of a 30-year bond's life, that may not be the case anymore unless they dramatically alter their budgets. At the end of the day, ratings are one aspect of due diligence. They are useful screening devices, but you need to understand who you are lending money to by purchasing bonds and diversify your holdings to protect your wealth.  The problem, of course, is when the trustees of your pension fund invests in garbage assets after getting a sales pitch on the beach in Hawaii, then conveniently place all of the blame for that bad investment on the rating agency. You unfortunately have zero control over that." "I like Muro questions! No, I don't think they do.  Because for me, as a personal finance investor type just trying to save for retirement, they mean nothing. If I cannot tell what the basic business model of a company is, and how that business model is profitable and makes money, then that is a ""no buy"" for me.  If I do understand it, they I can do some more looking into the stock and company and see if I want to purchase. I buy index funds that are indexes of industries and companies I can understand.  I let a fund manager worry about the details, but I get myself in the right ballpark and I use a simple logic test to get there, not the word of a rating agency. If belong in the system as a whole, I could not really say.  I could not possibly do the level of accounting research and other investigation that rating agencies do, so even if the business model is sound I might lose an investment because the company is not an ethical one.  Again, that is the job of my fund manager to determine.  Furthermore and I mitigate that risk by buying indexes instead of individual stock."
I don't know of any books, but there are a lot of good white papers on the subject if you take the time to look for them. For example, Moody's has a white paper on their LGD model (LossCalc) that explains their calibration methodology.   Searching for academic papers on the subject is really the only way to go, because credit risk is a field that really is just being explored. Really only since 2006 have banks started to actively try to use a risk rating model that incorporates PD and LGD. This is because of data insufficiency - banks just didn't keep active and centralized loan level data that is required to calibrate the models.  tl;dr: Use the internet - it is your friend. "If you need less than $125k for the downpayment, I recommend you convert your mutual fund shares to their ETF counterparts tax-free: Can I convert conventional Vanguard mutual fund shares to Vanguard   ETFs? Shareholders of Vanguard stock index funds that offer Vanguard ETFs   may convert their conventional shares to Vanguard ETFs of the same   fund. This conversion is generally tax-free, although some brokerage   firms may be unable to convert fractional shares, which could result   in a modest taxable gain. (Four of our bond ETFs—Total Bond Market,   Short-Term Bond, Intermediate-Term Bond, and Long-Term Bond—do not   allow the conversion of bond index fund shares to bond ETF shares of   the same fund; the other eight Vanguard bond ETFs allow conversions.) There is no fee for Vanguard Brokerage clients to convert conventional   shares to Vanguard ETFs of the same fund. Other brokerage providers   may charge a fee for this service. For more information, contact your   brokerage firm, or call 866-499-8473. Once you convert from conventional shares to Vanguard ETFs, you cannot   convert back to conventional shares. Also, conventional shares held   through a 401(k) account cannot be converted to Vanguard ETFs. https://personal.vanguard.com/us/content/Funds/FundsVIPERWhatAreVIPERSharesJSP.jsp Withdraw the money you need as a margin loan, buy the house, get a second mortgage of $125k, take the proceeds from the second mortgage and pay back the margin loan. Even if you have short term credit funds, it'd still be wiser to lever up the house completely as long as you're not overpaying or in a bubble area, considering your ample personal investments and the combined rate of return of the house and the funds exceeding the mortgage interest rate.  Also, mortgage interest is tax deductible while margin interest isn't, pushing the net return even higher. $125k Generally, I recommend this figure to you because the biggest S&P collapse since the recession took off about 50% from the top.  If you borrow $125k on margin, and the total value of the funds drop 50%, you shouldn't suffer margin calls. I assumed that you were more or less invested in the S&P on average (as most modern ""asset allocations"" basically recommend a back-door S&P as a mix of credit assets, managed futures, and small caps average the S&P). Second mortgage Yes, you will have two loans that you're paying interest on. You've traded having less invested in securities & a capital gains tax bill for more liabilities, interest payments, interest deductions, more invested in securities, a higher combined rate of return. If you have $500k set aside in securities and want $500k in real estate, this is more than safe for you as you will most likely have a combined rate of return of ~5% on $500k with interest on $500k at ~3.5%.  If you're in small cap value, you'll probably be grossing ~15% on $500k. You definitely need to secure your labor income with supplementary insurance.  Start a new question if you need a model for that. Secure real estate with securities A local bank would be more likely to do this than a major one, but if you secure the house with the investment account with special provisions like giving them copies of your monthly statements, etc, you might even get a lower rate on your mortgage considering how over-secured the loan would be. You might even be able to wrap it up without a down payment in one loan if it's still legal.  Mortgage regulations have changed a lot since the housing crash." "This is the best tl;dr I could make, [original](https://www.bloomberg.com/news/articles/2017-09-21/s-p-lowers-china-s-rating-to-a-from-aa-says-outlook-stable) reduced by 87%. (I'm a bot) ***** &gt; S&amp;P Global Ratings cut China&amp;#039;s sovereign credit rating for the first time since 1999, citing the risks from soaring debt, and revised its outlook to stable from negative.  &gt; &amp;quot;It&amp;#039;s bad optics for China, especially when they&amp;#039;re out there from a policy and rhetorical standpoint talking about debt more and acknowledging their debt challenge,&amp;quot; said Andrew Polk, co-founder of research firm Trivium China in Beijing.  &gt; The International Monetary Fund last month increased its estimate for China&amp;#039;s average annual growth rate through 2020, while warning that it would come at the cost of rising debt that increases medium-term risks to growth.   ***** [**Extended Summary**](http://np.reddit.com/r/autotldr/comments/71j6ih/sandp_cuts_chinas_credit_rating_citing_risk_from/) | [FAQ](http://np.reddit.com/r/autotldr/comments/31b9fm/faq_autotldr_bot/ ""Version 1.65, ~214028 tl;drs so far."") | [Feedback](http://np.reddit.com/message/compose?to=%23autotldr ""PM's and comments are monitored, constructive feedback is welcome."") | *Top* *keywords*: **China**^#1 **debt**^#2 **rate**^#3 **S&amp;P**^#4 **growth**^#5" "This is the best tl;dr I could make, [original](https://www.bloomberg.com/news/articles/2017-05-25/investors-say-it-s-time-to-price-climate-into-cities-bond-risks) reduced by 95%. (I'm a bot) ***** &gt; Municipal defaults are rare: Moody&amp;#039;s reports fewer than 100 defaults by municipal borrowers it rated between 1970 and 2014.  &gt; Kurt Forsgren, a managing director at S&amp;P, said its municipal ratings remain &amp;quot;Largely driven by financial performance.&amp;quot; He said the company was looking for ways to account for climate change in ratings, including through a city&amp;#039;s ability to access insurance.  &gt; Laskey, of Fitch, was skeptical that rating companies could or should account for climate risk in municipal ratings.   ***** [**Extended Summary**](http://np.reddit.com/r/autotldr/comments/6ejcgp/rising_seas_may_wipe_out_these_jersey_towns_but/) | [FAQ](http://np.reddit.com/r/autotldr/comments/31b9fm/faq_autotldr_bot/ ""Version 1.65, ~133538 tl;drs so far."") | [Theory](http://np.reddit.com/r/autotldr/comments/31bfht/theory_autotldr_concept/) | [Feedback](http://np.reddit.com/message/compose?to=%23autotldr ""PM's and comments are monitored, constructive feedback is welcome."") | *Top* *keywords*: **rated**^#1 **climate**^#2 **risk**^#3 **bond**^#4 **change**^#5" From Dimson, Elroy, Paul Marsh, and Mike Staunton. Triumph of the Optimists: 101 Years of Global Investment Returns. Princeton, N.J: Princeton University Press, 2002: Disappointingly, the small firm effect has not proved the road to   great riches since soon after its discovery, the US size premium went   into reverse. This was repeated in the United Kingdom and virtually   all other markets around the world. Despite their disappointing performance in recent years, the very   long-run record of small-caps remains one of outperformance in both   the United States and the United Kingdom. Furthermore, mid- and   small-size companies are still an important asset class. Their   differential performance over long periods of history shows that there   is useful scope for investors to reduce risk by diversifying across   the “large” and the “small” capitalization sectors of the market.   Furthermore, given the pervasiveness of the size effect across the   entire size spectrum, it is important to all investors since the   size tilt of any portfolio will strongly influence its short- and   long-run performance. This holds true whether there is a size premium   or a size discount. The size effect has certainly proved persistent   and robust. What is at issue is whether we should continue to expect a   size premium over the longer haul. And accompanying charts:    And one chart from BlackRock: If you are interested in this stuff, S&amp;P produce a sovereign rating methodolgy, in which they will tell you exactly what factors they look at.  Once you read this, you can obtain their latest rating report on India and Spain to understand how they applied said methodology in each case. (Not sure if this is free) It has been talked about extensively. It is talked about in [Crisis Economics](http://www.amazon.com/Crisis-Economics-Course-Future-Finance/dp/1594202508) by Nouriel Roubini.   Basically, what he wants to change is the people that own the security being rated are the ones that pay for the rating. This would help to eliminate some of the bias because they are being paid by people that want to know as much information about the security that they own.  I think it's something that would require government action to occur (could be wrong) which is why the business model hasn't changed. "Mortgage agreements usually have a clause in which the mortgagor warrants that all the statements and information which they have provided to the mortgagee are correct. In your case, this probably included your credit score. Since your ""statement"" concerning your credit score is no longer accurate, they want you to update the agreement with the new information before the final version is prepared. Credit scores change for many random reasons. The agencies re-calibrate formulas constantly. It is unlikely that your mortgage negotiations affected your credit score. The bank will only start reporting the facts of mortgage to a credit agency when you start paying (or not paying) the loan. Credit agencies don't care whether you have a loan or not. They only care whether you have paid your debts, or not paid them."