“Layer, highlight, repeat”

Communicating your work in a presentation is an essential skill in most professional fields. However, slide-show tools like Powerpoint are often seen as “necessary evils”, because they are frequently used badly.

Kieren Healy, a sociologist and data visualization expert, has a nice primer on how to make effective slides. One strategy in particular, “layer, highlight, repeat”, is something that I have found to be effective, but I’d simply never had a name for it. In his words:

One straightforward but effective technique is to build up your argument, your data, or your findings, by layering, content, highlighting new elements, and repeating methods of presentation or design elements so that your audience can follow the logic of what you’re saying.

Just as we guide our audience through our thought process by verbal explanation, we want to reinforce this with an appropriate visual metaphor. The “layer, highlight, repeat” strategy works more often than not because it maintains the thread between slides, helping the audience along.

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What we need is a 9-cent coin

Lately I’ve been thinking about coins. They may be going out of style around the world, but where I am at least they are still a fact of daily life. After fumbling around with coins at the cashier trying to find the right change, I’ve often wondered whether we can improve a currency by changing the denomination of the coins.

For example, we encounter prices ending in .99 more often than, say, .37. Wouldn’t it make sense to have a 99-cent coin? How would one even go about trying to answer this question?

It took a long train ride with no Internet connection for me to sit down and start hacking out an answer. Other people have tackled it before (pdf), but there were some aspects that I felt were still left unexplored.

I’ve put my thoughts and explorations online at this website. In the process, I’ve come to a few conclusions:

  • The coins of the US dollar are not really rationally designed, but they are not bad when it comes to making change, in the trade off between the number of different types of coins, and the average number of coins needed to make change.
  • The optimal denomination that uses three coins is 1, 9, 30. This is when the real-life distribution of prices is taken into account.

I hope that you enjoy reading my analysis as much as I have had in working out the problem.

Changer-ranger – Fun with the optimal change problem

DIY Soy Milk

To use up some soy beans that had been lying around the house for too long, I decided to try making some soy milk. The recipe is really easy – the only special equipment you’ll need is a blender. It’s a fun project for a weekend afternoon, and by making your own you can control for example how much sugar goes into the drink.

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Seven tons of old coins

The South China Morning Post had a feature this past October on Werner Burger, an expert on old Chinese cash, and his collection of seven tons (!) of coins stored in a warehouse in Hong Kong. Burger recently published a door-stopper of a book on cash in the Qing dynasty, following up on his first book from 1975.

Chinese coin from the Qianlong era of the Qing dynasty

Chinese coin from the Qianlong era of the Qing dynasty. (By Murberget Länsmuseet Västernorrland [Public domain], via Wikimedia Commons)

My father had a copy of the latter at home, and I remember thinking that it was merely a collector’s guide. I had no idea that this work was based on (just a part of) his collection of 2 million coins. The story of how Burger came into possession of these coins is also fascinating – a friend of his in Hong Kong was importing old Chinese cash from Indonesia to use as scrap metal, and let him pick out some for himself.

Since his 1975 book, which covered the Qing dynasty up to the beginning of the Qianlong emperor’s reign, new archival material from the imperial mint has been discovered. Burger used his collection and the archival material to reconstruct the fiscal history of the era, in order to analyze why Chinese currency became so devalued during the Qing.

What a wonderful story of serendipity and sheer persistence! Cash is such a fascinating thing – at once a physical artefact and an abstract idea, a ritual item (in the anthropological sense) that most people handle every day, somewhat mystical and yet mundane.