  It is instructive to consider stylized figures for the parameters on the right-hand-sides of equations (18) and (19), respectively. Although stylized, they are figures for the pair of ethical parameters \(\sigma\) and \(\delta\) that economists who have written on the economics of climate change have assumed in their work. To be sure, the welfare economics of climate change has demanded more complicated models than the model that is represented in equations (1) and (11a), but as we confirm below, it has not offered any additional theoretical insights. In what follows we take a year to be the unit of time and assume that \(\mu = 0.05\) (i.e., 5% a year). Along the optimum, the consumption rate of interest equals the rate of return on investment (the Ramsey Rule), which means that the optimum consumption rate of interest equals a constant 5% a year.