Tag Archives: holidays

Why you see Christmas items in stores during the summer: a story about supply chains

I confess that I don’t mind Christmas items in stores before Thanksgiving. While I agree that it’s too early, I understand why it’s sometimes a good business decision. Christmas items are similar to other “perishable” items like newspapers, produce, blood, and fashion, that go bad after Christmas in this case. These supply chains are managed differently than the supply chains for non-perishable items. Anna Nagurney has some excellent posts on perishable supply chains, blood banks, and blood supply chains.

I discovered an article about this by Kori Rumore in the Chicago Tribune that goes into detail about Christmas supply chains. Below I list a few supply chain observations I thought about or learned when reading the article. I use “Christmas” here generically because “holiday” is ambiguous, although other winter holiday items are often included with Christmas items (Christmas items make up the bulk).

  1. Christmas and holiday items are seasonal items in stores. Many box stores have a fairly large section dedicated to only seasonal items, where they put out many items for the next season. A typical seasonal section may rotate through the following merchandise: Valentine’s Day, Easter/spring, summer/beach, back to school, Halloween, and Christmas items. After Halloween, the next “season” associated with a lot of merchandise is Christmas. It’s better to stock the seasonal section with Christmas items than let it remain empty.
  2. Some stores like craft stores also have to deal with the crafting supply chain: you have to make holiday decorations well in advance of the holiday, so the holiday craft supplies need to be available for purchase crazy early. Christmas craft supplies often come out in the summer. I’m a regular at the craft store, but this never fails to surprise me.
  3. Seasonal items can sell out, so many consumers like to shop early while there a selection of items, and retailers have an incentive to cater to early shoppers (even if this irks most shoppers).
  4. The holiday items you see in the summer may be a tiny fraction of what you will eventually see after Thanksgiving, when the bulk of Christmas items grace store shelves. Some retailers only put out a few select items, such as collector’s items. The US Postal service and Hallmark sell to stamp and ornament collectors, respectively, and they put out Christmas items early for the collectors, not non-collectors like me. It had never occurred to me that I might not be the target audience for those early Christmas items.

The Chicago Tribune notes that 40% of consumers like to start holiday shopping before Halloween. I am one of them, but I usually shop for gifts, not holiday items. I’m a bargain hunter and usually buy holiday items like cards and wrapping paper when they are deeply discounted (the day after Christmas).

On a final note, supply chains are not why stores sometimes play Christmas and holiday music before Thanksgiving. There is no excuse for that 🙂

Where have you seen many Christmas items for sale?


a Christmas brain teaser

When finding some math worksheets to occupy my six year old daughter on her day off of school, I discovered a Christmas brain teaser for elementary students (in pdf format):

Find a route [between twelve cities] for Santa to follow that is as short as possible. After you have found a route, compare it to others to see if they found a shorter route.

Of course, you will immediately recognize this as the TSP.  The “solution” is amusing:

Try to view this question as open-ended, or your student(s) might be working on it for days. …And if someone figures out the best answer to this question, please let me know and I’ll add it here.

Finding the optimal solution to a twelve city TSP is indeed pretty hard.  So hard, in fact, that the folks at math-drills.com couldn’t find the solution.  I have confidence that my readers can find the optimal solution in less than a day.  But please spend Christmas with your families enjoying holiday cheer.

Happy holidays!

Christmas cookies (and a recipe)

Just for kicks, I decided to take a few pictures of my Christmas cookies this year.  I usually try to make cookies efficiently.  Often, that means bar cookies, since they are uber-efficient (but not pretty).  But this year, I made real cookies that required molding, rolling, cutting, and pressing.  I didn’t use a constraint programming approach, but I did enlist the help of my two daughters to make and decorate the cookies.  My cookies this year include:

My cookie tasters (i.e., my daughters) loved the new almond crescent cookie recipe that we came up with.  I posted it here.  There are some obvious substitutions that will probably work, but I’ll let you use your imagination in that department.  I wrote this recipe from memory, so if I there is an mistake, let me know and I’ll fix it.

Almond crescents


  1. 3/4 cup ground almonds
  2. 1 3/4 cups flour
  3. 1/4 teaspoon salt
  4. 1/3 cup brown sugar
  5. 1 stick (1/2 cup) Earth Balance spread
  6. 1/3 cup canola oil
  7. 1 teaspoon almond extract
  8. 1/2 teaspoon vanilla extract
  9. Soymilk as needed
  10. 1 cup powdered sugar
  11. cinnamon to taste


  1. Preheat the oven to 375 degrees Fahrenheit.
  2. Mix the dry ingredients (#1-4).  Cut the dry ingredients with the Earth Balance until it resembles crumbs.
  3. Add the oil, extracts, and soymilk and stir until the mixture more or less sticks together.
  4. Take tablespoon-sized amounts of dough and form into crescents.  They don’t rise much, so you can put them close together on the cookie pan.
  5. Bake for 14-16 minutes.  Don’t let these cookies brown. While they are baking, mix the powdered sugar and the cinnamon (I used about 3 big shakes, but more would be better) in a bowl.
  6. Let the cookies cool on the pan until they are warm.  Remove the cookies and cover them with the powdered sugar mixture.

Happy holidays!

Almond crescents

Almond crescents. My kids ate most of them before I was able to take a picture.

Peanut butter blossoms

Peanut butter blossoms

Chocolate spritz cookies

Chocolate spritz cookies

Kolacky, Kolache, Kolachy, Kolach

Kolacky cookies

not a Latin square

I decided to sew a quick Advent calendar earlier in December to ration candy consumption in the house.  Advent calendars have 24 pockets/doors/hooks/etc. for accessing Christmas treats (I prefer chocolate).  I sewed my Advent with five colors of felt.  When I was done, I looked at it and immediately thought that I should have added a 25th pocket, arranged the squares in a five-by-five grid, and assigned the colors according to a Latin square.  Oh well. That is a project for another year.

Advent calendar

The advent calendar that should have been the first Latin square Advent calendar

The chromatic number of Christmas tree is 4: on graph coloring problems over the holiday

I enjoy the holiday season.  I unashamedly celebrate Christmas, and I enjoy decorating the house for the holidays.  This year, I used graph coloring problems to help me decorate.  If you are not familiar with graph coloring, consider a graph with a set of vertices and edges.  The goal is to assign a color to each vertex such that no two connected vertices have the same color and such that the fewest number of colors are used (the chromatic number).  One application is to create maps, such as this one of the United States.

How does graph coloring relate to Christmas decorating? I’ll give you an example. I have had an intense desire for the past 17 years or so to decorate my Christmas tree using only a few, beautifully coordinated colors (like red/silver/gold or purple/silver) rather than throw on a bunch of ornaments of every color like I always do. But I’d decorate the tree OR style, by hanging exactly one ornament on each branch and requiring that adjacent branches have different colors. This in essence imposes a graph coloring problem on my tree decorating.  The chromatic number of a planar graph is 4.  I suppose that the chromatic number of a conic graph (i.e., a Christmas tree) is also four, since a conic graph can be cut along one side to become a plane.  I am not sure if the edges removed to turn the cone into a plane would be problematic, but I doubt it (graph theorists, please leave a comment!).

The reason I have never colored my Christmas tree is that I am sentimental and feel the need to hang all of my favorite ornaments on the tree, regardless of their color. With young kids who create a few new ornaments every year of various colors that don’t fit any of my Christmas tree decorating fantasies, I always thought that I would never color my Christmas tree in the near-future. Or so I thought.

This year, I bought a Christmas tree-shaped centerpiece that requires a gumdrop to be placed on the end of each branch (it is pictured below, along with my Christmas tree).  I examined the centerpiece, and noticed that all of the branches lie in a vertical line, which should allow me to use as few as two colors.  I opted for three (red, green, white), but my daughters insisted on using purple, too.  The best part was when I explained the concept to my six year old, and she was really jazzed by the extra challenge (a future graph theorist?)  When the tree was four-colored, my ~3-year old added a few yellow and orange gumdrops to some of the extra branches, so now the tree has six colors.  But I think there’s a good chance that she will eat the yellow and orange gumdrops at some point, bringing the tree back to four colors as we had originally intended.

On a related note, I once had a conversation about vertex coloring over a bag of Valentine M&Ms.  Valentine M&Ms have four colors whereas holiday M&Ms have three colors, and if you’re eating M&Ms with another nerd, it eventually leads to a discussion of the types of graphs whose chromatic numbers are equal to the number of M&M colors.  I suppose this is the type of problem one nerd has if they eat candy with another nerd, but it’s a good problem to have.

This blog post contributes to the INFORMS monthly blogging theme.  Look for the INFORMS blog to summarize the blogs at the end of the month.

What are your favorite graph coloring results?

My 6-colored Christmas tree centerpiece

My 6-colored Christmas tree centerpiece



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