Description for Diagram 3.1
Standard and pseudo populations and samples

Diagram showing two figures. The first figure illustrates a standard population and sample at time $t-1$  and $t.$  Populations at time $t-1$  and $t$  are overlaid. The rectangle is divided in three horizontal parts $–$  the death, the common and the birth populations. Sample at time $t-1$  is represented as a subset of population at time $t-1.$  It's made of units from the common and death populations. Sample at time $t$  is represented as a subset of population at time $t.$  It's made of units from the common and the birth populations. The two samples partially overlap: some common population's units selected at time $t-1$  are also included in the sample at time $t.$

The second figure illustrates a pseudo-population and its sample at time $t-1$ and $t.$ At time $t,$ time $t-1$ and time $t$ pseudo-populations are defined as the union of the standard population at time $t-1$ and at time $t.$ At time $t,$ these two pseudo-populations contains the same units. Samples at times $t-1$ and $t$ are made of units from the common, birth and death populations. Sample at time $t$ is partially overlapping with the one at time $t-1.$