We all build products based on assumptions - assumptions about our users, who they are, how they think, what they expect. When the underlying assumptions underpinning product design no longer holds, new opportunities are created.

Jakob Nielsen, a famed user experience researcher, writes about one such secular dislocation of UX assumptions in the Anti-Mac interface. It’s a post written in 1995 that remains remarkably relevant today. It contemplates all the assumptions underpinning the original Apple software design, and how the old fundamentals no longer apply for users who have grown up with technology. Below, I’ve reproduced all the core Mac UI assumptions from 1995. How many of them changed with the smartphone just ten years later?

The Macintosh was designed under a number of constraints, including:

It needed to sell to “naive users,” that is, users without any previous computer experience.

It was targeted at a narrow range of applications (mostly office work, though entertainment and multimedia applications have been added later in ways that sometimes break slightly with the standard interface).

It controlled relatively weak computational resources (originally a non-networked computer with 128KB RAM, a 400KB storage device, and a dot-matrix printer).

It was supported by highly impoverished communication channels between the user and the computer (initially a small black-and-white screen with poor audio output, no audio input, and no other sensors than the keyboard and a one-button mouse).

It was a standalone machine that at most was connected to a printer.

Because millennials will constitute 75% of the US workforce within the next ten years, software built on outdated principles like the ones above won’t survive. Users simply won’t adopt them. In fact, users will reject them outright. How many companies have migrated from on-premise Exchange to Gmail because younger users have demanded that UI? Or Slack instead of email? Or Dropbox instead of a Windows shared drive? Or RelateIQ instead of Salesforce?

The vast majority of a millennial user base is dextrous with software. Consequently, their expectations of it are much greater. Multiplatform, mobile, simple and logical UI, anticipatory software powered by machine learning.

The underlying assumptions of how software should be designed are changing faster and faster. These UX and technology dislocations create a broad new set of opportunity for startups, especially bottoms up SaaS startups whose user acquisition strategy usually relies on word of mouth growth. Companies simply can’t have software built on outdated assumptions about users and succeed.

Sometimes these assumptions are invalidated suddenly, an abrupt discontinuity. The smartphone altered the interactions preferences of hundreds of millions of people in just a few years. Other times, the assumptions change more slowly, for example, with generational changes, and like the proverbial boiled frog, we are much less likely to be aware of these secular dislocations even if they are just as impactful.

Every once in a while, it’s worth asking, which assumptions does your product have about its users? And how many of them have changed in the last few years?