The silliest thing is Zengerle's casual assumption that if the free and peaceful exercise of an enumerated constitutional right "takes up resources," then the state may therefore limit it. I doubt he'd like to generalize this principle.

Of course! But so what? This fact tells us nothing about the causal impact of income on test scores. [...] This graph is a good example of omitted variable bias, a statistical issue discussed in Chapter 2 of my favorite textbook. The key omitted variable here is parents' IQ. Smart parents make more money and pass those good genes on to their offspring. [...] It would be interesting to see the above graph reproduced for adopted children only. I bet that the curve would be a lot flatter.

I don't know of any large studies that test the relationship between test scores and socioeconomic status in adopted children. But the closest adoption study described in Richard Nisbett's Intelligence and How to Get It: Why Schools and Cultures Count (I'll put the full citation at the bottom) has this to say about IQ and socioeconomic status (SES):

The obvious point to make here is that children born to wealthy parents and raised by downscale families have almost exactly the same IQ range as children born to downscale parents and raised by wealthy families. Nisbett uses this to make what I thought would have been an entirely uncontroversial point -- namely, that "both genes and class-related environmental effects are powerful contributors to intelligence"

And is it really hard to figure out why those "class-related environmental effects" should make a difference? Better schools, better nutrition, better health care, better test preparation and better neighborhoods all come to mind. I'm sure an intelligent guy like Greg Mankiw can figure that out.

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(John Sides reports on some other studies and makes some good points here. The chart above is drawn from Capron & Duyme, "Assessment of Effects of Socioeconomic Status on IQ in a Full Cross-Fostering Study" (1989).)

FOX News' Glenn Beck is doing an extraordinary job this week walking America behind the scenes of 1600 Pennsylvania Avenue and outlining who is actually running the White House.

Monday night he asked us to invite one friend to watch; tonight I invite all my friends to watch.

corporation, trust, or community chest, fund, or foundation [...] organized and operated exclusively for religious, charitable, scientific, literary, or educational purposes, or to foster national or international amateur sports competition (but only if no part of its activities involve the provision of athletic facilities or equipment), or for the prevention of cruelty to children or animals.

The "strong" version of the supply side argument is that tax cuts will generate enough growth to increase tax revenue. (Not to be confused with the general Laffer Curve proposition that tax cuts can do this, which will probably be true under some circumstances -- say, if a tax rate went from 100% to 99%.) The "semi-strong" version is that tax rates are the key factor governing economic growth. And the "weak" version is that the growth and efficiency generated by lower taxes is more important than the equality generated by redistribution. (The "weak" version pretty much just restates the big difference between the left and the right, so it's really quite general.) 

You write that [Greg] Mankiw defines a supply-sider as "someone who believes in the general proposition that taxes affect incentives." You say that is a meaningless definition, though, because "Everyone believes that!"

This is not true, at least in an operational sense. The revenue-forecasting models used by the Joint Committee on Taxation and Treasury's Office of Tax Analysis are designed so that changes in tax policy - no matter how profound - have zero impact on the economy's growth rate. Double all tax rates? The economy will remain on the current path. Sweep away the internal revenue code and replace it with a low-rate consumption-based system like the flat tax? Doesn't matter, GDP will be unaffected.

So while the reasonable left is smart enough to admit that tax rates do affect incentives, they vigorously resist any effort to modernize the revenue-estimating system. Why? I suspect they understand that this would somewhat hinder the left's redistributionist agenda (at least to the extent to which it is financed by soak-the-rich tax policy).

I also would augment your characterization of strong, semi-strong, and weak versions of supply-side economics by adding the "somewhat-strong" version, which is that changes in marginal tax rates affect incentives and lead to changes in taxable income that can have a measurable impact on economic performance. I think it is fair to say that this is what most "supply siders" actually believe (which, to be sure, is different than what some overly-optimistic Republican politicians assert).

I don't know enough about revenue-forecasting to say much about the JCT. But while I'd merrily admit that tax cuts have an effect on incentives, it's not clear that the revenue estimates suffer to the detriment of your position for lack of a GDP component. (I am reminded of this old Jason Furman analysis.) But I shouldn't start an argument that I'd lose: Perhaps there is a widely accepted and more inclusive forecasting model that would be picked up by the government, if only there were less foot-dragging on the left.

On the taxonomy: Fair enough, although I think your somewhat-strong version would be pretty hard to distinguish from my weak version. Sure, taxes probably have a measurable impact on economic performance. But I imagine that someone on the intelligent left thinks the impact is smaller than you do, and someone on the intelligent left thinks the benefits of government reditribution are greater than you do. Or at least I believe that! (I described this difference, from your perspective, as "the growth and efficiency generated by lower taxes [are] more important than the equality generated by redistribution" -- and I hope that wasn't a cariacature. I really do think that's the best description of the reasonable economic policy differences between the right and the left.)

You have identified some of the key issues. Jason Furman types would agree that taxes affect incentives, but they would argue the effects are small. My counter response would be that even small changes in growth (say 1/10th of one percent annually) become very significant with the passage of time because of compounding.

But since we can't agree on the magnitude of those potential growth changes, we obviously would not have common ground on a model (assuming we could even overcome other methodological issues).

Shifting to taxonomy, your weak version is a good description of how the different sides approach the issue, but I don't think it captures my concern. The problem is not (at least in this context) that my counterparts on the left value redistribution more than growth. The problem is that the revenue-estimating system assumes that tax policy reforms have zero impact (not small impact, zero impact) on overall economic performance. So the reasonable left is allowed to sound, well, reasonable by admitting that tax policy can impact incentives, but those same people inevitably resist any reforms to the scoring process - even ones using their very modest assumptions about the magnitude of "supply side" effects.

I am especially troubled that they also seem uninterested in transparency. The JCT refuses to open its "model" to inspection (a step, I hasten to add, that in no way would compromise private taxpayer data). Why block public discussion and examination of the model, particularly by academics? Unless, of course, one has an agenda and fears that sunlight will make it impossible to defend the current system.

While the advertising boycott has generated substantial media coverage, Fox News said it has not impacted the network's revenues or Beck's audience. "The advertisers referenced have all moved their spots from Beck to other programs on the network so there has been no revenue lost," a spokeswoman said.

Obama's government-run health "reform" would pay for seniors' meetings with a doctor to discuss end-of-life care. While nonthreatening at first, something that is quite normal for a family to do becomes troublesome when the government gets involved. Seniors know that government programs that seem benign at first can become anything but. The government should simply butt out of conversations about end-of-life care and leave them to seniors, their families and their doctors.

If the Congressional Democrats can't get a health care package through, it won't prove that President Obama is a sellout or an incompetent. It will prove that Congress's liberal leaders are lousy tacticians, and that its centrist deal-makers are deal-makers first, poll watchers second and loyal Democrats a distant third. And it will prove that the Democratic Party is institutionally incapable of delivering on its most significant promises.

You have to assume that on some level Congress understands this -- which is why you also have to assume that some kind of legislation will eventually pass. [...] If it doesn't, President Obama will have been defeated. But it's the party, not the president, that will have failed.

Major legislative change is hard, so it should come as no surprise that Barack Obama's drive to comprehensively reform the American health-care system is running into some problems. By contrast, Monday-morning quarterbacking is easy, so it also should come as no surprise that these problems are inspiring a massive wave of second-guessing.

[...] It's possible that despite the formidable obstacles, Obama will prevail in the end. Already he's come closer than any of his predecessors. But it's also possible that he'll fail, and if so, there won't be anything unusual about it. [...] Time and again presidents and their supporters learn the main lesson of American policymaking -- that for better or for worse, our system makes big changes difficult to implement.

Morally, everyone of us would like to cover every American with health insurance but that's where you spend most of the trillion dollars plus, or a little less that is estimated, the estimate said this health care plan will cost. And I'm afraid we've got to think about putting a lot of that off until the economy is out of recession. There's no reason we have to do it all now.

MCCAIN:  Well, I think that what we are talking about here is do -- are we going to have groups that actually advise people as these decisions are made later in life and ...

STEPHANOPOULOS:  That's not in the bill.

MCCAIN:  But -- it's been taken out, but the way that it was written made it a little bit ambiguous.