12
May
2018
The Primary Determinants of Your Child’s Weight
“They just grow up so fast…” said one of the parents as we watched the graduation ceremony.
People talk like this a lot, but there’s really no mystery about the size of your child, once we specify the units (such as pounds). School lunch policy drives the growth in class calorie consumption, and the growth in class calorie consumption (divided by the number of kids per class) is by far the most important determinant of child weight gain. (The other determinant is the ratio of child weight gain to total class calorie consumption.)
I mean, once you spell it out like that, it’s all crystal clear why the kids are growing at the rate they are.
For more clarifications like this, check out EconLog.
From Sumner:
It kind of works, but there’s times when it doesn’t (e.g. 2013). Not entirely a bad rule of thumb to keep in mind.
https://fred.stlouisfed.org/graph/fredgraph.png?g=jPQf
When you look at other related factors in the economy, nominal wage growth is one of the least volatile, so Krugman doing a big hand wringing exercise over a tiny change in nominal wage growth is kind of silly to begin with. The actual value of those USD in terms of commodities has been the most volatile factor of all, which means perhaps we should be spending a bit more time looking at the currency situation, because that’s where the action is at.
I would argue that the brief burst of nominal wage growth in 2009 when other economic factors were falling does not properly agree with either Sumner or Krugman, but probably represents employers laying off their least productive employees while hanging onto the best people. Hence hours worked overall is falling but hourly rates for the remainder seem to be growing only because the mix of people is changing. That’s the problem with aggregate statistics, they rarely say what you think they are saying.
Beautiful!
I am not sure where you are going with this.
” School lunch policy drives the growth in class calorie consumption,…”
If you mean calorie consumption is the classroom, for which we can read “school”, this may be true.
“…and the growth in class calorie consumption (divided by the number of kids per class) is by far the most important determinant of child weight gain. ”
This is clearly not the case. Calorie consumption in school is not the most important determinant in child weight gain.
Are you saying there is something equally a=obviously wrong with the NGDP statement?
“Monetary policy drives NGDP growth, and NGDP growth (per worker) is by far the most important determinant of nominal wage growth. (The other determinant is labor share of GDP.)”
In the weight gain case there are two other determinants: calories taken outside school and calorie use.
How much food the cafeteria puts on a plate is based (in part) on how much food they think kids need. How much food kids need is based (in part) on how fast they are growing. How fast they grow is based (in part) on how much food they eat.
How fast NGDP grows is based in part on how fast wages grow (in almost all models). How fast wages grow is based in part on X (depending on the model) and how fast X grows is based in part on how fast NGDP grows.
There is no causality in these models absent the extremes. Yes your kid will stop growing if you don’t feed them enough, and they will balloon up and have major health issues if you force feed them 10,000 calories a day, to stretch the analogy weight = calories in – calories out, but calories out is effected by calories in + genetics+ environment + etc. If CBs turn off the money supply then the economy will starve, if they force it up ridiculously high then it will bloat, but that doesn’t imply that NGDP is controlled by the CB, and it does not imply that some portion of NGDP like wage growth is directly tied and can be boosted by driving up NGDP.
Aw shucks Dr. Murphy, my hero, Scott Sumner, unwavering advocate for market driven monetary, has endeavoured to educate us about the significant differences between the real economy and the nominal economy. Sure, the analogy is funny but only when the you are willing to let the distinction between real and nominal become blurred.
Market driven monetary policy