where C(j + 1, i) is a combinatorial with repetition of i out of j + 1 years. We use
expression (A.1) to build net intakes series based on enrolment data. The right-hand
side of (A.1) is a function of three parameters: the repetition rate (r), the dropout rate
(d) and the net intake growth rate (n). In the stationary state, primary enrolment Et
grows at the same rate as net intakes. Thus n may be computed from the enrolment
growth rate. One particular case is when d = r = n = 0. In this case, Et = Nt × P
and so the number of new entrants is simply equal to the pupils enrolled in primary
education divided by its duration. UNESCO provides estimates for repetition and
survival rates in primary schooling for most countries in the world starting in 1970.
The survival rate (which is defined as the percentage of students enrolled in the first
grade that are expected to reach the final grade) is used to compute the dropout rate.
Defining s as the survival rate and noting that,