In reality there are practical difficulties in objectively measuring utility. Although money might be used as a unit of measurement, to do so we must assume that money itself is subject to constant utility as any unit of measurement must be constant in value. However, it would be reasonable to assume that money is also subject to diminishing marginal utility. For instance, an extra £1 on top of a weekly income of £100 would be more valued than that same extra £1 on top of an income of £500. Nevertheless, despite problems of measurement, the concept of diminishing marginal utility remains consis- tent with consumer experience