Let's Decide

Home : Software : an iOS application by Trevis Rothwell, last updated in January 2011

Going out for dinner with friends? How about a movie afterwards? But how ever will you decide which restaurant and which theater? Gordon wants fish and science fiction, Cesar wants lasagna and comedy, Laura wants tacos and documentary...

You can use this application to arrive at a decision between multiple options, taking into account how you and your friends rank all of the options.

Enter the options to decide between
Enter the names of the people voting
For each person, arrange the options in their preferred order

The application can then display the result of combining everyone's preferences using a borda count preference schedule algorithm.

Borda Count

There are multiple ways of tallying up votes in an election. "Majority rules" is perhaps the most simple, and in many cases may be adequate. Looking only at which option has the most first-place votes, though, totally ignores other aspects of voter preferences. The borda count voting method looks not only at first-place votes, but the ranking of every option being considered. As such, it is useful in many everyday decision-making tasks.

For example, imagine that you and ten coworkers are going out for lunch, and have to decide between three restaurants. If five of you most prefer restaurant A, three of you most prefer restaurant B, and three of you most prefer restaurant C, then a majority-rules election would pick restaurant A. But what if the six people who most preferred restaurants B and C ranked restaurant A last? Then while a clear majority of five people most prefer restaurant A, a clear majority of six people least prefer restaurant A. Perhaps selecting restaurant B or C would be more agreeable to everyone.

Can There Be A Tie?

Depending on what options are entered and how the voters arrange their preferences, there can be a tie between two or more options. If this happens while you are using the application, you can eliminate some of the options that clearly are not going to win and run the preferences again, with fewer options.

If there are already very few options (for instance, two of them) such that removing any wouldn't make any sense, then you might consider adding more options. One limitation of the borda count algorithm is that it becomes decreasingly useful as there are fewer options or fewer voters. In an extreme case of one voter with one option, there is clearly no reason to use the borda count method at all: just select the one option.

Further Study

For more information on various voting methods, including borda count, take a look at this episode of For All Practical Purposes.

Additional Credits

Tab icons in application generously provided by Glyphish.

Title graphic and main application icon designed by Bruce Rothwell.

License

The software is licensed to the public under the GNU GPL.

Get the source code.

Purchase Application

This application is available on the Apple iTunes application store. Buy one today! Better yet, buy a thousand!

tjr@acm.org