Public Good needs to be considered in our decisions?

In economics , the marginal utility of a good or service is the utility gained (or lost) from an increase (or decrease) in the consumption of that good or service. Economists sometimes speak of a law of diminishing marginal utility , meaning that there are diminishing returns in consumption, so that the first unit of consumption of a good or service yields more utility than the second and subsequent units. In economics , a public good is a good that is non-rivalrous and non-excludable . Non-rivalry means that consumption of the good by one individual does not reduce availability of the good for consumption by others; and non-excludability that no one can be effectively excluded from using the good. [1] In the real world, there may be no such thing as an absolutely non-rivaled and non-excludable good; but economists think that some goods approximate the concept closely enough for the analysis to be economically useful