The circles at the top of the graphic represent age classes of a pension system, with 20-year-old new hires at the left and the elderly retired shuffling off this mortal coil at the right. The translucent circles are payments, with premium payments flowing down into the pension fund and benefit payments going back up. The reddish coins falling into the piggy bank are premium payments and the orange coins are investment income. The funding ratio is shown to the right, but you can also tell from how full the piggy bank looks. If you hold your mouse over one of the age class circles, you can see some information about that class. The population used here is a sample of a much larger population, so the age classes will seem small.
What you see here is a model system, built using financial, mortality, and member data sampled from the CalSTRS system, as of 2013, with a much lower asset level for illustration purposes. It tries to incorporate the uncertainty and randomness of the real world, though does not attempt to incorporate real-world investment results. Obviously, no model can capture all the complexity of a real system, but there is a fully-functional, actuarially sound model behind this graphic display that can be applied to the demographics and financial circumstances of any specific pension system.
Click on the image to pause the animation.