System Usability Measured Over Time: An Exploratory Descriptive Study
Philip T. Kortum, Claudia Ziegler Acemyan, Frederick Louis Oswald · International Journal of Human-Computer Interaction · 2026
This article characterizes the subjective usability of 14 common, everyday products using the System Usability Scale (SUS) over time in an exploratory study. Products evaluated included Microsoft Excel, Microsoft Word, Microsoft PowerPoint, handheld GPS systems, digital video recorders, the Nintendo Wii, the iPhone, Amazon.com, ATM’s, Gmail, microwaves, landline telephones, Internet browsers, and Google search. A total of 1618 users were queried about the usability of these products using an online survey methodology over the course of 8 years, from 2009 to 2016. Results showed that nearly all products (except for MS Excel) showed some form of linear trend in usability over time. Exactly half of the products (MS Word, MS PowerPoint, iPhone, ATMs, DVRs, Amazon.com, and Landline telephones) showed statistically significant trends over time at the 0.10 statistical significance level, with some (MS Word, MS PowerPoint, iPhone and Amazon.com) exhibiting increased usability over time, and others (ATMs, DVRs and Landline telephones) showing decreased usability over time. Potential reasons for these trends, including feature addition, feature stagnation, or market success, are discussed.