Tree decorations by the numbers

Just in time for Christmas, a group of math students at the University of Sheffield, in the UK, has calculated the number of decorations, the height of the star, and the length of tinsel and lights you need for the perfect Christmas tree. And they've posted a plug-in formula so you can avoid the math.

I'm not sure what "perfect" means in this context (the screenshot is a still from the Debenham's TV ad, which you can watch here). The formula is based on the height of the tree and defaults to 140 centimeters, which is about 4.5 feet.

For a 4.5 foot tree, they say, you need 29 baubles, a 5.5 inch star, and about 14.5 feet of lights.

For a bigger tree, say 8 feet (my converter says that's 244 cm) you'd need 50 baubles, a 9.5 inch star, and about 25 feet of lights.

Trying this out makes me see some ratios - the star has been set at about 10% of the height of the tree. What happens when you try out the formula? Any thoughts on why height, not surface area or volume, is the basis? Have you ever not put all your ornaments on the tree? Have you even counted them? Send pictures!