This week's Apple Worldwide Developers Conference was notable for its format (virtual) and its announcements (hundreds of new features covering the entire product line).

The Apple keynote also had something for anyone creating and delivering a business presentation--a design strategy to make slides cleaner and easier to read in a virtual setting.

Use an average of just three words per slide.

During the nearly two-hour event, I counted 21 slides that only contained text. Most slides had one or two words, others contained a sentence of five or six words, and one slide had as many as 13 words.The average is three.

For example, Apple CEO Tim Cook made the big announcement that the company's Mac line of computers will transition from Intel to Apple's own processor.

One of Cook's slides read: "Historic Day."

Another slide read: "Apple Silicon."

Other slides read: "Two-Year Transition" and "First system by end of year."

Researchers have found that we can't multitask as well as we think we can. Too many words on a slide confuses the audience, because it's nearly impossible to read the paragraph, listen to the speaker, and absorb the message at the same time.

Since packing more words on a slide requires a smaller font, text-heavy slides are also hard to read, especially on a computer screen in a virtual setting.

While there is no hard data on the ideal number of words on a slide, former Mac evangelist Guy Kawasaki has a rule that no slides should have less than 30-point font. In fact, Kawasaki's former boss--Steve Jobs--used 190-point font. The bigger the font, the fewer words on a slide.

I tried to replicate some of the slides I saw on the WWDC 2020 keynote. Much of the text was designed in 190-point font and larger.

For example, Apple's director of Siri data science, Yael Garten, said in the keynotes that Siri is receiving 25 billion requests each month and now has 20x more facts than just three years ago. She showed the numbers on two different slides; each statistic took up more than half the screen.

While we don't know for sure how many words the average presentation slide has, some researchers have put the number at 40. That seems about right. If that's the case, it means an Apple presenter would have to show 13 or 14 slides before reaching the number of words an average presenter has on just one slide.

In other words, your PowerPoint slides are probably too wordy. Yes, I know Apple uses its propriety presentation software (Keynote), but this design tip applies to any presentation: Use fewer words to get your message across.