Saturday, July 26, 2014

Reign of Error

I recently read "Reign of Error" a 2013 book by Diane Ravitch about American public schools.  There are two main factions in US education debates.  The traditional educational establishment as exemplified by the teacher unions which largely supports more of the same and the "reformers" who believe that major changes are needed including replacement of many of the current teachers.  In this book Ravitch presents the establishment case, defending the status quo and attacking the reformers and their proposals.  As long time readers of this blog know I am not a fan of either side in this debate.  Nor did I particularly like this book.  While I generally agree that the reform proposals are wrongheaded I sometimes found her arguments against them unconvincing.  And I don't think her own proposals make a lot of sense.

The problem with the traditional educational establishment is that they have a grossly inflated opinion of themselves.  They believe teachers are very important and therefore deserving of lots of pay and respect.  While these views are understandable in union leaders it makes it difficult for them to respond effectively to the reform arguments that since teachers are so critical to the educational process society should expend much more effort in identifying and weeding out bad teachers and that this would significantly improve our schools.

In truth however teachers aren't very important in that (within the range commonly found in US schools) they have little influence on results.  It matters much more who the student is (again within the range commonly found in US schools) than who the teacher is.  Peers also have more effect on outcomes than teachers.  This means it is difficult to distinguish between below average and above average teachers and that the payoff for replacing below average teachers with above average teachers is not all that large.  So the reformer's obsession with replacing large numbers of current teachers makes little sense.  Slightly below average teachers are difficult to identify and are not doing much harm anyway.   

One way in which differences among students matter is that some students are brighter than other students.  The establishment (including Ravitch in this book) ignores this (apparently for political correctness reasons).  Of course any system for evaluating teachers that doesn't take ability differences into account will be grossly unfair but the establishment's unwillingness to acknowledge that ability differences exist handicaps their response. 

As noted above I didn't always think Ravitch made the anti-reform case very well.  She goes on about how factors beyond a teacher's control (like a parental divorce) can affect student results and that how this makes evaluating teachers on the basis of results unfair.  But this is unconvincing.  What matters is how the inevitable random noise compares to the differences in teaching ability you are trying to detect.  As it happens because these differences are relatively small random noise is a significant issue making ranking individual teachers problematic.  Note student rankings are subject to random noise too but because the differences in performance are relatively larger they are more reliable.

Ravitch also goes on about how charter schools can be more selective about their students.  This is a legitimate point in so much as if charter schools are only admitting bright students this should be accounted for in evaluating their results.  But if charter schools are gaining by excluding disruptive students this is a legitimate advantage which should not be discounted. Keeping disruptive students in mainstream public school classes is a policy decision that could be reversed.  If it has bad effects it is perfectly legitimate to count them against public schools.  Similarly placing students of widely varying ability in the same classes is a policy decision.  If charter schools can do better by tracking again this is a legitimate advantage that should be acknowledged.

I also wasn't convinced by Ravitch's own proposals.  She goes on and on about all the things schools should teach besides the basic reading, writing and arithmetic skills students need to function as adults.  This is fine for the top students who can pick up the basic skills quickly and with little effort but problematic for those who can't.

Ravitch also advocates expanded preschool programs the benefits of which are not as well established as she claims.  She cites the Perry Preschool Project in a misleading way:

... At the time, many people assumed that IQ was fixed and that interventions made no difference.  Weikart set out to prove them wrong.

One might think from this and her subsequent discussion that the Project had succeeded in raising IQ.  But in fact while the Perry Preschool Project claims many wonderful results raising IQ (permanently) is not one of them.  See the discussion at page 16 here:

It is true that the High/Scope Perry Preschool program had a statistically significant effect on children’s IQs during and up to a year after the program, but not after that.  ...

As for the other results one small 50 year old study is not entirely convincing.  Some replications would be nice.

And Ravitch wants to reserve certain positions for professional educators.  But being a professional educator is a lot like being a professional astrologer.  There is no underlying generally accepted scientific body of knowledge involved.  So I see no reason to give "professional educators" and their politically correct fad theories of the moment undue deference.

The book did have some interesting material.  For example it presented data showing that test scores have improved somewhat over the last 30-40 years.  If correct (I have not attempted to independently evaluate and verify this claim) this is a worthwhile corrective to the widespread gloom and doom stories.

But overall this book is pretty long and I didn't find it very interesting.  I don't recommend it.

Thursday, July 17, 2014

No Money Down

Felix Salmon recently revisited an argument (Stern v. Salmon) he had with Linda Stern 3 years ago about buying a house with little money down.  Without attempting to address every point in dispute I believe Stern is largely correct.  If it makes sense for you to buy a house, but you haven't saved a large down payment, but you can get a mortgage on reasonable terms anyway, then it generally makes sense to buy a house now with little money down rather than waiting to save a large down payment.

Salmon's biggest mistake is a complete failure to understand that the main effect of a larger down payment is to protect the lender (and society at large) not the borrower.  It does so by reducing the value of the "homeowners put" (the option to walk away from an underwater mortgage, which contrary to Salmon you don't have to be broke to exercise (at least in no recourse states)), which like any put is more valuable when the market price is close to the strike price.  This means low down payment mortgages should be very expensive or unobtainable.  They aren't because they are subsidized by the government.  Salmon ignores this subsidy which obviously affects the analysis when he claims that banks are not charitable institutions.

This doesn't mean everyone who can obtain a mortgage should buy a house, transaction costs are extremely high so you should be confident that you won't need or want to move soon.  But if buying a house with 20% down would make sense then I expect it will usually still make sense with a lower down payment.

Friday, July 11, 2014

The Frackers

I recently read "The Frackers" a 2013 book by Gregory Zuckerman which is mostly about men who backed the development of hydraulic fracturing (aka fracking), a technology which has produced large unexpected increases in domestic (US) oil and natural gas production.  I found the book somewhat disappointing.  It basically is a collection of stories about some of the colorful figures involved.  It jumps from person to person and back and forth in time in a way that I found a bit confusing.  And it seems very weak on the big picture, in the mass of detail it is hard to tell which events were significant and which turned out to be unimportant.

One point I found of interest is that many of the investors in the technology appeared to be driven more by blind faith than any rational calculation of the odds.  And in some cases they were curiously blind to the fact that if the technology was as successful as they hoped the resulting increases in production would drive down prices particularly for natural gas (whose market is more local to the United States).  As a result a couple of them got badly overextended and didn't do as well from the success of the technology as one might have expected.

Overall however while this is an important story I don't think this book does a very good job of telling it.  Too much human interest detail and not enough big picture analysis.