Claasen's logarithmic law of usefulness is named after technologist Theo A. C. M. Claasen, who introduced the idea in 1999 when he was CTO of Philips Semiconductors:

Usefulness = log

Logarithm

The logarithm of a number is the exponent by which another fixed value, the base, has to be raised to produce that number. For example, the logarithm of 1000 to base 10 is 3, because 1000 is 10 to the power 3: More generally, if x = by, then y is the logarithm of x to base b, and is written...

(Technology)

The law can also be expressed as:

Technology = exp

Exponential function

In mathematics, the exponential function is the function ex, where e is the number such that the function ex is its own derivative. The exponential function is used to model a relationship in which a constant change in the independent variable gives the same proportional change In mathematics,...

(Usefulness)

Examples of Claasen's law

System parameters (e.g. RAM, CPU speed, disk capacity) need to increase by a multiple to create a noticeable impact on performance.

A modern car (e.g. a Ford Mondeo) is not substantially more useful at getting the occupants from A to B than an older car (e.g. a Ford Model T)

Claasen's law in combination with Moore's law

In order to achieve a linear improvement in usefulness over time it's necessary to have an exponential increase in technology over time. Moore's law

Moore's Law

Moore's law describes a long-term trend in the history of computing hardware: the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years....

delivers an exponential increase in technology, and so when Classen's law is combined with Moore's law it implies a linear improvement in usefulness over time.