CLOSE
ThinkStock/Erin McCarthy
ThinkStock/Erin McCarthy

What’s the Deal with Those Last 4 Digits on ZIP Codes?

ThinkStock/Erin McCarthy
ThinkStock/Erin McCarthy

Almost everyone knows their five digit ZIP code, and probably a few others within their city, but what’s up with the extra four digits you sometimes see on mail?

Let’s start with those first five digits you’re already familiar with. In the early 1960s, the U.S. Postal Service could see that the old Postal Delivery Zone System was outdated and couldn’t handle increasing mail volume and urban and suburban expansion. To keep the mail moving efficiently, the Postal Service introduced the Zone Improvement Plan (ZIP) in 1963. A five-digit code was assigned to every address in the country—the first designated a broad geographical area or group of states (“1,” for example covers New York, Pennsylvania, and Delaware), the next two designated a region or large city in that area (“91” covers Philadelphia) and the last two represented a smaller delivery zone or group of delivery addresses in that region. 

Over the next two decades the ZIP system became strained, too, and in 1983, the Postal Service expanded it to create the ZIP+4 system, tacking on an extra four digits at the end of the old codes. These new digits identified an area—like a group of apartments or office buildings—or a high-volume mail receiver within a five-digit delivery zone to help with mail sorting and delivery. The sixth and seventh digits of a ZIP+4 indicate a “delivery sector,” like a group of streets, P.O. boxes, a group of buildings, or even a single high-rise building. The eighth and ninth digits designate a “delivery segment,” like a specific side of a street, a floor in an office or apartment building, or a specific department within a large office. 

Getting the public on board with the regular old ZIP codes had been hard enough (some people were annoyed they had another number to remember in addition to telephone area codes and their Social Security number, while others thought that being represented by a number was dehumanizing and un-American), so the ZIP+4 never caught on with people. Fortunately, around the time the expanded codes were implemented, the technology available to the USPS meant that people didn’t have to remember or use the full code. Automatic mail sorting systems apply a Postnet barcode to mail items that corresponds to a full code, and multi-line optical character readers can determine the correct ZIP+4 from the barcode and written address. 

nextArticle.image_alt|e
iStock
arrow
Big Questions
Why Does Turkey Make You Tired?
iStock
iStock

Why do people have such a hard time staying awake after Thanksgiving dinner? Most people blame tryptophan, but that's not really the main culprit. And what is tryptophan, anyway?

Tryptophan is an amino acid that the body uses in the processes of making vitamin B3 and serotonin, a neurotransmitter that helps regulate sleep. It can't be produced by our bodies, so we need to get it through our diet. From which foods, exactly? Turkey, of course, but also other meats, chocolate, bananas, mangoes, dairy products, eggs, chickpeas, peanuts, and a slew of other foods. Some of these foods, like cheddar cheese, have more tryptophan per gram than turkey. Tryptophan doesn't have much of an impact unless it's taken on an empty stomach and in an amount larger than what we're getting from our drumstick. So why does turkey get the rap as a one-way ticket to a nap?

The urge to snooze is more the fault of the average Thanksgiving meal and all the food and booze that go with it. Here are a few things that play into the nap factor:

Fats: That turkey skin is delicious, but fats take a lot of energy to digest, so the body redirects blood to the digestive system. Reduced blood flow in the rest of the body means reduced energy.

Alcohol: What Homer Simpson called the cause of—and solution to—all of life's problems is also a central nervous system depressant.

Overeating: Same deal as fats. It takes a lot of energy to digest a big feast (the average Thanksgiving meal contains 3000 calories and 229 grams of fat), so blood is sent to the digestive process system, leaving the brain a little tired.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

nextArticle.image_alt|e
Getty Images
arrow
Big Questions
How Are Balloons Chosen for the Macy's Thanksgiving Day Parade?
Getty Images
Getty Images

The balloons for this year's Macy’s Thanksgiving Day Parade range from the classics like Charlie Brown to more modern characters who have debuted in the past few years, including The Elf On The Shelf. New to the parade this year are Olaf from Disney's Frozen and Chase from Paw Patrol. But how does the retail giant choose which characters will appear in the lineup?

Balloon characters are chosen in different ways. For example, in 2011, Macy’s requested B. Boy after parade organizers saw the Tim Burton retrospective at the Museum of Modern Art. (The company had been adding a series of art balloons to the parade lineup since 2005, which it called the Blue Sky Gallery.) When it comes to commercial balloons, though, it appears to be all about the Benjamins.

First-time balloons cost at least $190,000—this covers admission into the parade and the cost of balloon construction. After the initial year, companies can expect to pay Macy’s about $90,000 to get a character into the parade lineup. If you consider that the balloons are out for only an hour or so, that’s about $1500 a minute.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios