Archive for the ‘mere empirics’ Category

#bern nevada

The  basic truth of politics is that incumbents have huge advantages and those favored by incumbents also have an advantage. Thus, the fundamentals favor a candidate like Hillary Clinton over Bernie Sanders.It’s not an iron clad law, but it is a big factor that shapes most political races.

The presidential primary, in both parties, the process can be about four months long and it is very complex. Historically, the winners rarely knock out all opponents in the early states of Iowa and New Hampshire. Usually, early states weed out weak candidates and leave only two or three serious competitors who “settle” the election on Super Tuesday. You have to go back about 40 years, to the 1960 election, to find a primary where candidates where struggling into the summer. Since the birth of the modern primary system in the 1970s, those who lead after Super Tuesday tend to win it all since it is hard to overcome the delegate lead at that point.

So that is where Nevada fits in. Previously an unimportant state, Nevada is now important. Sanders needs to keep a positive narrative going into Super Tuesday so that he can continue to fund raise and swamp the Clinton campaign in the media and on the ground in the Super Tuesday states. A tie or loss in Nevada would dampen things and make it harder to sway Black voters in South Carolina, who might only defect in sufficiently large numbers after a Sanders win. Also, a Nevada win could soften the blow of a close loss in South Carolina since Sanders could claim that he’s 2-2 againt HRC.  In other words, Sanders needs a chain of wins to overcome the advantages that Clinton has in terms of name recognition and access to easy money. If Nevada #Berns this weekend, then I will see it as the first actively visible sign that the Democratic party is tipping away from the DLC/Clinton centrist faction of the 1990s. Until then, “advantage incumbent.”

50+ chapters of grad skool advice goodness: Grad Skool Rulz ($2!!!!)/From Black Power/Party in the Street

Written by fabiorojas

February 19, 2016 at 12:01 am

bmi – a conceptual mess, or, andrew perrin i take back what i said earlier

One of the basic measures of health is body mass index (BMI). It is meant to be a simple measure of a person’s obesity which is also correlated with morbidity. Recently, I spent some time researching the validity of BMI. Does it actually measure fatness? The answer is extremely confusing.

If you google “validity of BMI as a measurement of obesity,” you get this article that summarizes a few studies. The original definition of obesity is that you need to have at least 25% body fat for men and 35% for women. This is hard to measure without special equipment, so BMI is the default. Thus to measure BMI validity, you need a sample of people and then compute the BMI and the body fat percentage (BF%). The reports that in number of studies compared BF% and BMI. In some ways, BMI survives scrutiny. In non-obese people, as defined by BF%, BMI works well, but it seems to under-report obesity in others. In a few odd cases, mainly athletes with a lot of muscle weight, obesity is over-reported. Thus, you get a lot of mis-classification: “One meta-analysis on the subject suggests that BMI fails to classify half of persons with excess body fat, reporting them as normal or overweight despite having a body fat percentage classifying them as obese.” Translation, we are much fatter than we appear to be.

Then, soon after I read some of these studies, the LA Times reported on a new study from UCLA that examines the BMI-morbitiy correlation. In that study, researchers measured BMI and then collected data on biomarkers of health. This is done using the NHANES data set. See the study here. Result? A lot of fat people are actually quite healthy in the sense that BMI is not associated with cardio-pulmonary health (i.e., your heart stopping). This reminds me of an earlier discussion on this blog, where there were conflicting estimates of the obesity-mortality link and a meta-analysis kind of, sort of, shows an aggregate positive effect.

How do I approach the BMI issue as of today?

  • BMI is a rough measure of fatness (“adiposity”), but not precise enough for doctors to be making big judgments about patients on a single number/measurement.
  • BMI is not a terribly good predictor of mortality, even if there is a mild overall correlation that can be detected through meta-analysis.
  • BMI is probably not correlated with a lot of morbidity that we care about with some important exceptions like diabetes.

The lead author of the UCLA study said that this was the “last nail in the coffin” for BMI. She might be right.

50+ chapters of grad skool advice goodness: Grad Skool Rulz ($2!!!!)/From Black Power/Party in the Street

Written by fabiorojas

February 18, 2016 at 12:01 am

will the texas primary stop the #bern?

The Obama strategy in 2008 had a plan A and a plan B. Plan A was to knock out Hillary with big victories in Iowa and New Hampshire. Didn’t work. Plan B was to pad the delegate lead by exploiting small state caucuses and minimizing the damage in Hillary friendly places like New York. That worked, especially since the Hillary campaign was simply incompetent.

Sanders has a similar plan. His Plan A, the early knock out, almost worked. I suspect that Bernie might have even won the popular vote in Iowa, given that the Iowa Democratic Party is refusing to release vote tallies as they did in previous years. So Bernie is on to Plan B. That means he has to accomplish two things:

  • Max out caucus states.
  • Minimize losses in large primary states.

This is the list of remaining states in February and Super Tuesday and delegate totals for Democrats according to US election central:

  • Alabama 60
  • American Samoa caucus 10
  • Arkansas 37
  • Colorado caucus 79
  • Georgia 116
  • Massachusetts 116
  • Minnesota caucus 93
  • Nevada 43
  • Oklahoma 42
  • South Carolina 59
  • Tennessee 76
  • Texas 252
  • Vermont 26
  • Virginia 110

You will notice that Bernie has at least three easy states: Vermont, Massachusetts, and probably Minnesota. Then, it gets really hard, really fast. This is not because Hillary will magically become a great campaigner, but the fundamentals favor Hillary.

There are two reasons. First, you win Southern states in the Democratic primary by doing well among Black voters. South Carolina (Feb 27) will be the first test of how well Bernie can move these voters. If he comes up short in South Carolina, it’s bad news because you have more Southern states coming up real fast  such as Alabama and Georgia on Super Tuesday and other Southern states soon after that. Second, in March, you will see the types of big states that Hillary dominated in 2008 because of superior name recognition, such as Texas (51% for HRC in 2008), New York (57%), California (51%), Ohio (53%), and Pennsylvania (54%).

Is it impossible for Bernie to win the nomination? Of course not, but he needs to really dominate outside of the establishment friendly mega-states like Ohio and California. That means an immediate and massive turn around in the Black vote, a wipe out in the caucus states, and some strategy for containing the losses from the big states, which even challenged Obama. That sounds really hard to me.

50+ chapters of grad skool advice goodness: Grad Skool Rulz ($2!!!!)/From Black Power/Party in the Street

Written by fabiorojas

February 11, 2016 at 12:01 am

does piketty replicate?

Ever since the publication of Piketty’s Capital in the 21st Century, there’s been a lot of debate about the theory and empirical work. One strand of the discussion focuses on how Piketty handles the data. A number of critics have argued that the main results are sensitive to choices made in the data analysis (e.g., see this working paper). The trends in inequality reported by Piketty are amplified by how he handles the data.

Perhaps the strongest criticism in this vein is made by UC Riverside’s Richard Sutch, who has a working paper claiming that some of Piketty’s major empirical points are simply unreliable. The abstract:

Here I examine only Piketty’s U.S. data for the period 1810 to 2010 for the top ten percent and the top one percent of the wealth distribution. I conclude that Piketty’s data for the wealth share of the top ten percent for the period 1870-1970 are unreliable. The values he reported are manufactured from the observations for the top one percent inflated by a constant 36 percentage points. Piketty’s data for the top one percent of the distribution for the nineteenth century (1810-1910) are also unreliable. They are based on a single mid-century observation that provides no guidance about the antebellum trend and only very tenuous information about trends in inequality during the Gilded Age. The values Piketty reported for the twentieth-century (1910-2010) are based on more solid ground, but have the disadvantage of muting the marked rise of inequality during the Roaring Twenties and the decline associated with the Great Depression. The reversal of the decline in inequality during the 1960s and 1970s and subsequent sharp rise in the 1980s is hidden by a fifteen-year straight-line interpolation. This neglect of the shorter-run changes is unfortunate because it makes it difficult to discern the impact of policy changes (income and estate tax rates) and shifts in the structure and performance of the economy (depression, inflation, executive compensation) on changes in wealth inequality.

From inside the working paper, an attempt to replicate Piketty’s estimate of intergenerational wealth transfer among the wealthy:

The first available data point based on an SCF survey is for 1962. As reported by Wolff the top one percent of the wealth distribution held 33.4 percent of total wealth that year [Wolff 1994: Table 4, 153; and Wolff 2014: Table 2, 50]. Without explanation Piketty adjusted this downward to 31.4 by subtracting 2 percentage points. Piketty’s adjusted number is represented by the cross plotted for 1962 in Figure 1. Chris Giles, a reporter for the Financial Times, described this procedure as “seemingly arbitrary” [Giles 2014].9 In a follow-up response to Giles, Piketty failed to explain this adjustment [Piketty 2014c “Addendum”].

There is a bit of a mystery as to where the 1.2 and 1.25 multipliers used to adjust the Kopczuk-Saez estimates upward came from. The spreadsheet that generated the data (TS10.1DetailsUS) suggests that Piketty was influenced in this choice by the inflation factor that would be required to bring the solid line up to reach his adjusted SCF estimate for 1962. Piketty did not explain why the adjustment multiplier jumps from 1.2 to 1.25 in 1930.

This comes up quite a bit, according to Sutch. There is reasonable data and then Piketty makes adjustments that are odd or simply unexplained. It is also important to note that Sutch is not trying to make inequality in the data go away. He notes that Piketty is likely under-reporting early 20th century inequality while over-reporting the more recent increase in inequality.

A lot of Piketty’s argument comes from international comparisons and longitudinal studies with historical data. I have a lot of sympathy for Piketty. Data is imperfect, collected irregularly, and prone to error. So I am slow to  criticize. Still, given that Piketty’s theory is now one of the major contenders in the study of global inequality, we want the answer to be robust.

50+ chapters of grad skool advice goodness: Grad Skool Rulz ($2!!!!)/From Black Power/Party in the Street

Written by fabiorojas

February 10, 2016 at 12:01 am

the cuban victory in the republican party

A number of writers noticed that we overlooked an important bit of news last week during the Iowa caucus – two Latinos and a Black man took 60% of the Iowa GOP caucus. At the very least, this is newsworthy and merits explanation.

Here’s how we should understand the rise of Rubio and Cruz. The basic elements of minority party politics are as follows:

  • African Americans started in the GOP but moved to the Democratic party.
  • Groups that were forcibly assimilated into the US tend to go Democrat – Native Americans, Mexicans, Filipinos.
  • Groups that benefited from Cold War politics tend to lean GOP more than others – Vietnamese, Cubans.
  • Other voluntary migrants vary but if they are harassed or repressed they lean Democrat.

Using these rules of thumb, it is easy to see how Cruz and Rubio make a path to the top of the GOP. They are Cubans, who have influence in the GOP, especially in Florida. They are also from states with strong GOP parties – Florida and Texas. As many folks have noted, they downplay their ethnic background as well and kowtow to the anti-immigration crowd. Briefly, Rubio endorsed some sort of compromise on immigration but walked that back.

The rise of these two candidates does not represent a big swing of Latino voters to the GOP – that would only happen if large numbers of Mexicans defect from the GOP. It does however reflect an opening made possible by the complex history of US foreign relations. In the messy world of Cold War politics, the US chose to favor Cubans and, decades later, their children are steps away from the White House. And oddly, Castro might be alive to see it!

50+ chapters of grad skool advice goodness: Grad Skool Rulz ($2!!!!)/From Black Power/Party in the Street

Written by fabiorojas

February 8, 2016 at 12:01 am

#bern toast

As of 10:45 pm, Hillary Clinton maintains a slim lead over Bernie Sanders in the 2016 Iowa Caucus. In terms of absolute performance, Sanders fans should be happy. When all votes are tallied, Sanders will either win the caucus or lose by a very slim margin. That means that Sanders will continue. He’ll win New Hampshire and make it to Super Tuesday and probably win a few more states.

However, in terms of winning the nomination, this is tough for Sanders. The reason is that Clinton is the party’s candidate and about 45% of voters in the Democratic party are extremely comfortable with her. They will only defect in sufficiently large numbers if they see that she is indeed crumbling and they need an unambiguous signal. If 2008 is any guide, Hilary can reliably depend on 40% – no matter what happens. Even after it was abundantly clear in 2008 that Clinton did not have a reasonable chance at catching Obama in the delegate count, she still kept winning big states like California, Pennsylvania and Ohio – by large margins (but not enough to make up for earlier losses).

Adding to the problem for Sanders is that Obama’s strategy – maxing out caucus states – only works once. Clinton’s campaign simply wasn’t prepared for it and they weren’t prepared for a campaign that went beyond Super Tuesday. They are prepared this time, poorly perhaps, but prepared. The close race in Iowa shows it.

Here’s the bottom line. When you fight the party’s candidate, you need to seriously knock them down to break the view that they are invincible. Obama did that with a completely unexpected 8% victory. A near miss or narrow victory by Sanders does not do that, so it will be very, very hard to trigger a mass migration that needs to happen over the next month for a Sanders win.

50+ chapters of grad skool advice goodness: Grad Skool Rulz ($2!!!!)/From Black Power/Party in the Street 

Written by fabiorojas

February 2, 2016 at 4:01 am

racial biases for low and higher performing students

Former BGS Yasmiyn Irizarry’s research on how teachers treat students of different races is featured in Scientific American’s podcast. From the Social Science Research article:

Education scholars document notable racial differences in teachers’ perceptions of students’ academic skills. Using data from the Early Childhood Longitudinal Study-Kindergarten Cohort, this study advances research on teacher perceptions by investigating whether racial differences in teachers’ evaluations of first grade students’ overall literacy skills vary for high, average, and low performing students. Results highlight both the overall accuracy of teachers’ perceptions, and the extent and nature of possible inaccuracies, as demonstrated by remaining racial gaps net literacy test performance. Racial differences in teachers’ perceptions of Black, non-White Latino, and Asian students (compared to White students) exist net teacher and school characteristics and vary considerably across literacy skill levels. Skill specific literacy assessments appear to explain the remaining racial gap for Asian students, but not for Black and non-White Latino students. Implications of these findings for education scholarship, gifted education, and the achievement gap are discussed.

Check it out.

50+ chapters of grad skool advice goodness: Grad Skool Rulz ($2!!!!)/From Black Power/Party in the Street 

Written by fabiorojas

January 15, 2016 at 12:01 am


Get every new post delivered to your Inbox.

Join 3,720 other followers