Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
This paper models the costs of collecting whole blood in the north of Scotland in order to investigate strategies whereby the annual collection target can be met at lower cost. Data on the costs of the individual sessions held in 1993–1995 are analyzed using multilevel analysis. A new technique, namely the conditioned iterative generalized least squares (CIGLS) estimator is applied. Then the feasibility of collecting increased volumes from particular panels and areas is assessed by examining which factors determine the number of blood donors at a session. Results show that fixed cost and marginal cost vary across panels but marginal cost does not vary by volume. This implies that the cost‐minimizing policy is to equalize marginal costs and collect higher volume at fewer panels (those with lower fixed costs). The level of donations can be increased by increasing the number of opportunities to donate and/or increasing the average length of a session. The latter policy is shown to be more cost‐effective. Multilevel analysis proves not only to be appropriate but also particularly useful. © 1998 John Wiley & Sons, Ltd.