Friday, July 5, 2013

Growth of Obesity in the US: an Animated GIF

From the Centers for Disease Control and Prevention. Fairly self-explanatory.  More than a third of adults are now obese in this country (and over half are overweight, meaning that for the first time, over half of Americans respond to the term "Lardface").  Could this be in part because we are eating 60% more added oil and 40% more added sugar than we were 60 years ago

Thursday, June 20, 2013

Volume of People

A coworker recently texted me from a conference asking the volume of a sphere that would contain the world's population.  xkcd's "What-if?" has already addressed the area that would be required for everyone to stand (Rhode Island), but now we can stack people.

My question for this was how comfortable the people in my sphere are. There are some seven billion people in the world. In New York City, apartments must be at least 400 square feet, although new "micro-apartments" will be 300 SF.  Let's assume each person on the planet lives in a 300 SF studio. With 8-foot ceilings and two feet of structural floor, that's 3,000 cubic feet per person.  For all seven billion people, we'd need nearly 150 cubic miles of building, so our giant sphere apartment building would be 6.5 miles in diameter.  Let's say 7 miles if we allow for elevators and hallways.
Like the Technosphere, only 100 times as wide

What if the sphere was instead a future spaceship making some trip to another planet or star system? Cruise ship cabins get as small as 85 SF while Amtrak's sleeper rooms are about 50 SF, and both of these can sleep two.  We'll also cut the floor height to 8 feet (with 7 foot ceilings).  Depending on the luxury of travel, our sphere needs to be 2.6 to 3.1 miles across now.  Maybe a little more if we have life support and engines.
Like a Borg sphere scout, but 6 times as wide. Slightly larger volume than a Borg cube, but definitely smaller than a Death Star.

What if the people didn't need to be alive? Instead, let's build a spherical hearse for our 7 billion.  People are all different sizes, but on average, our caskets will be 6' by 2' by 1'.  Now we're really saving room, and can fit everyone on the planet 0.57 cubic miles. Our sphere is just a hair above a mile in diameter.
Like if Harold Chasen got a hold of these concept cars, and also made them 500 times as wide.

"No," my coworker said. "He says it's less than a kilometer."  What??  I've stuffed the people about as tight as I can get them. The only way I can pack them tighter is... oh god.
 Only not with ice.
The volume of a person is about 66 liters, or 2.33 cubic feet.  If you liquefy the human race and pour them into a spherical tank, all of humanity will fit in a diameter of 0.6 miles -- like from the White House to the Washington Monument.
Now we just need to fill that sphere.

I still don't know why my coworker needed this answer.

Sunday, June 2, 2013

Income by Subway Station

In April, the New Yorker ran a piece about income inequality along each of the subway lines, in which they made an interactive graphic portraying the median household income (from census data) at each of the subway stops on the line selected. For example, this is their graph for the F line.

It is an interesting exercise and produces some potentially informative graphics.  However, in determining household income, the New Yorker used a... I'll be polite: "unusual" technique.  They simply used the income value for the census tract in which their coordinates for the subway station lay.  This results in a number of problems.

Census tracts must be between 1,200 and 8,000 people, and most in New York seem to be mostly in the 2,000 to 5,000 range.  They vary in size as population density changes, but in New York are generally 1/16 to 1/4 square mile -- on the order of 8 blocks.  Many of the subway stations, like Columbus Circle or Carroll St have entrances 3 blocks apart from each other and in two different districts.  This means that the New Yorker's analysis would produce different income values based simply on which stairway they chose to mark the station.  The amazing thing is that they celebrate these statistical artifacts:
$142,265—The largest gap in median household income between two consecutive subway stations on the same line (between Fulton Street and Chambers Street on the A and the C lines, in Lower Manhattan).
As a first correction, we should at least average all of the census tracts that actually have subway stairs in them.  But what about other nearby ones?  How far out should we go?  Should neighboring tracts count in our average the same amount as slightly more distant ones?

In my analysis (you can argue with me if you want), I created a linearly decaying income weighting function, out to 1/2 mile (2.5 avenues or 10 blocks in Manhattan).  What this means is that tracts with a center on top of a given station get full weight, those 1/4 mile away get half weight, and those 1/2 mile or more have no influence.  It is important to note that the weighting values in the average for the tracts are relative to the values for all other tracts for a given station.  So for example, if a station is surrounded by 6 tracts, all with centers 1/4 mile away, all 6 would count equally towards the station's average income.  If there's two at 1/4 mile and two at 3/4 mile, the closer ones will influence the average by three times as much as the farther ones.

Thus, I get a map with the following median incomes. I have not created a line-by-line graphic like the New Yorker, but the data's all there if someone wants to be clever (see borough names below).

You can also explore a full screen version of the map.

The first thing you'll notice is that the income along the lines is much smoother in this analysis. The Fulton-Chambers difference is now $50,000, not $142,000.  The really big differences that remain are for stops actually separated by large distances.  The 4 largest (I believe) are the 4/5's 86th-125th St difference of over $100,00; The 2/3's Chambers-14th of $65,000; the A/D's Columbus-125th of $65,000; and the F's York-E.B'way of almost $60,000 across the East River. The greatest change for stops that are actually near each other is on the Upper East Side, when the income drops from $158k-$133k-$91k-$43k-$29k on 77th-86th-96th-103rd-116th Streets.  And poor Sutter Avenue on the L remains $12,000 less than any of its neighbors or anywhere in Brooklyn.

Since this technique involved comparing the distance between every station to every census tract (using data from the American Fact Finder), I broke the analysis down by borough to avoid creating a truly gigantic matrix.  For Manhattan and the Bronx, this is fine because no one walks across the East or Harlem Rivers to catch a train.  In Brooklyn and Queens, there may be some loss of accuracy along the border, since for example, no Brooklyn tracts are counted in the Seneca Ave M station, but there are few stations where this could really have an impact, and the data do not seem unusual.

I will not claim that this is the best way to analyze.  Maybe I should have a larger or smaller decay distance than 1/2 mile.  Maybe I should have used a different decay function than linear.  Maybe no decay function at all and simply give every tract with centers within 1/2 mile of the station full weight.  Maybe I should have even divided the map up into Voronoi polygons with one station in each and assign each census tract to exactly one subway stop.  But at any rate, this analysis produces more realistic and informative result than the technique used by the New Yorker.

Friday, February 24, 2012

American Annual Food Consumption

According to a report by the USDA, Americans are eating a lot. The aggregate food supply in 2000 (the total produced and imported less exported) averaged to 3,800 calories per day per person. As I've written on, a substantial amount of this not actually eaten, but thrown away. The USDA estimates that 1100 calories per person per day are wasted, leaving 2,700 as actually consumed (recall the "based on a 2,000 calorie-diet" nutrition labels). This is 800 calories above the average in the '50s and 500 above that in the '70s. The composition has changed over time too.

We are eating a lot more oil -- 60% more than in the '50s.  An average household of four is eating 40 gallons of added oil each year, which doesn't count fats found naturally in foods such as whole meat, nuts, and dairy.
Annual consumption of added oils for a family of four.
Added sugars are also on the rise: a 40% increase over five decades.  Cane and beet sugars consumption dropped by a third, but were more than compensated by a 8-fold increase in corn syrup.  A household consumes on average 600 lb. of added sugars each year, with 22% of it from soda. This is nearly a thousand 12-oz bottles of pop.

Fruits and even vegetables are also eaten more now than in the '50s, but just by 20%.  This reflects the overall trend of more everything rather than healthier foods.  Meat consumption increased by 40%, which is driven largely by a more-than-tripling of chicken.  Each family consumes 1 + 1/3 pig and 3/5 of a cow each year, as
well as over 100 chickens.

When adding the fish to the total, each household consumes 780 lb of meat each year.  Assuming the same meat-vs-total-weight ratios of pork and beef, this corresponds to an equivalent of eight people.

As Fat Knowledge has mentioned several times, the whole Food Miles idea is overblown.  The report also shows that its cost low.  It average 4% of the total cost of the food -- the same amount as advertising.  The largest costs are labor (38%) and farm value (19%).

Wednesday, February 1, 2012

Green Stars

Go to any planetarium show and they will probably point out how some of the stars are different colors. Betelguese (Orion's shoulder) is a deep red, while Rigel (his knee) is blueish white. That's because the stars are glowing bodies that emit a distribution of radiation that more or less follows the black body curve. Cool objects like candles glow red, brighter ones like incandescent bulbs are orange-yellow, and really hot things like a welder's torch or lightning are blue-white. In fact, the colors themselves are described by the temperature (in Kelvins) of an object that would emit light of that shade. You can see in the color below the path of the black body curve.
But back to the original question? Why does it skip green?

Hotter objects emit more energy than cooler ones, and the peak frequency also increases, according to Planck's Law. So logically, at some point, the peak emission wavelength should pass through green. But as this excellent (allegedly kid-oriented) video describes, when that happens, we don't see green because of how our eyes see color.

Our eyes have three cones that detect three frequencies of light that our brain interprets as color vision. When the black bodies emit at a temperature that peaks in green, it's also sending out less (but still lots of) light at nearby frequencies (blue and red). So with all that light coming in, our brain sees the green-peaking stars as white.

Friday, October 14, 2011

96% of U.S. transportation powered by petroleum

With all the talk of alternative fuels, it sometimes helps to put a sense of scale on things. The growing prevalence of electric cars is one rational for basing the federal highway taxes to vehicle miles traveled rather than gas consumption (more on this in a coming post). In 20 years, some predict electric cars will make up 64% new sales, but in the near term this is not the case. Even if the experts are right and there are 3/4 million electric cars on the within five years, there are currently more than 137 million licensed passenger cars in the U.S.

This double pie chart depicts what fuels transportation in America (data from The Geography of Urban Transportation, p 278). No details like passenger miles or ton equivalents, but simply trillions of BTUs (the sum of all is 27,500). Gasoline and diesel together make up more than 3/4 of the total. Jet fuel and ship fuel are much smaller but not insubstantial shares. (I'm not sure how they count international journals; another paper I saw took all the usage for domestic trips and half for international.) Our running total is up to 96.4% thus far.

Now we get to the final 3.6% that is not derived from petroleum. By far the largest chunk of this -- 2/3 of the remainder -- is another fossil fuel: natural gas. Oh, like those dual-fuel cars and delivery trucks in those articles, you think. But no, this natural gas is burned to power pumps which push more natural gas through pipelines. (It's still transportation energy, even if there's no vehicle involved.) Another quarter of the small pie is electricity used for the same purpose. Lastly, the final sixth of the little pie, or 0.29% of all transportation energy, is used in non-petroleum vehicles that actually move, like we normally think of for transportation. Of this, almost nine-tenths is electricity for subways, commuter railroads, the electrified portions of Amtrak, and a couple electric trolley buses. The rest is for natural gas buses. For perspective, this total of .29% is less than the gasoline used by recreational boats.

What about the electric cars? Well, the table only goes down to the tenth of a trillion BTUs, and the electric cars just get lost in the rounding. The other news-maker, methanol, is similarly zero. Interestingly, this doesn't imply that biofuel is insignificant. The gasoline fraction includes Gasohol, or 10% ethanol. From an FHA report, it seems that 13% of all gasoline sales are from Gasohol [Table 8 ÷ (Table 2 Sum × 365)]. This means that ethanol usage accounts for three times the energy as all other non-petroleum sources for vehicles (not counting the pipelines).

Thursday, November 18, 2010

"Educational Presentations" for Big Pharm

Pharmaceutical companies have long been notorious for giving gifts to doctors, hoping to increase prescriptions of their drugs. Some states, including Vermont, have put severe restrictions on this practice. However, it remains perfectly legal for the companies to "employ" the doctors to give talks on the benefits of their drugs, paying them up to $200,000 a year, as reported by WNYC. Some of these doctors had even lost their practicing license because of convictions by some health departments, and "teaching" became their primary profession.

But if a doctor thinks a drug is effective, there's nothing wrong with him or her letting others know what he or she likes about it, right? It's win-win because the doctor gets paid and the drug company gets an "expert" giving recommendations, rather than just a spokesperson. However, it's not just candid advice.
[A presenting doctor] shows up at a restaurant in front of a group of doctors and leads them through a PowerPoint presentation about the benefits and side effects of Geodon. All of the almost 80 slides are written by Pfizer. Pfizer and other companies say they need to make sure all the content complies with Food & Drug Administration regulations. The rule is Schloss [the doctor] can’t go off script, even if he may know a lot about the drug that isn’t mentioned on the slides.
Some of the paid doctors even admit this. “A monkey can read the slides at this point. Well, a monkey that can read can read the slides,” said Stephen Friedes, a psychiatrist who was paid for several years to advise an antidepressant. He eventually quit for this reason, saying “there’s no freedom of speech and I have to say the party line, and it took away all the fun and all the educating aspects of it.”
Others defend the practice. Frank Lowe, of Columbia Medical, claims that
“When new drugs come out, the general doctor has no clue about the new product,” said Lowe. “You know, when I go out to Wichita, Kansas or Kansas City or Asheville, North Carolina, where there are no significant medical schools associated with them, I actually provide a real service in terms of education -- even if the talks are scripted.”
Of course, if the doctor has no clue about the product, how is he or she a voice of authority? And if the talks are scripted, then why does an expert need to present them? Why can't a drug company advertising agent, or even a monkey who can read?