  A continuous variable changing between 0 and 1 is introduced to characterise
contentment, or satisfaction with life, of an individual and an equation
governing its evolution is postulated from analysis of several factors likely
to affect the contentment. As contentment is strongly affected by material
well-being, a similar equation is formulated for wealth of an individual and
from these two equations derived an evolution equation for the joint
distribution of individuals' wealth and contentment within a society. The
equation so obtained is used to compute evolution of this joint distribution in
a society with initially low variation of wealth and contentment over a long
period time. As illustration of this model capabilities, effects of the wealth
tax rate are simulated and it is shown that a higher taxation in the longer run
may lead to a wealthier and more content society. It is also shown that lower
rates of the wealth tax lead to pronounced stratification of the society in
terms of both wealth and contentment and that there is no direct relationship
between the average values of these two variables.
