For non-commercial robbery, Cook (1976) argued that robbers make strategic choices according to (1) their potency (‘firepower’) in generating a convincing threat and overcoming the victim’s resistance and (2) the perceived vulnerability, availability and attractiveness of the potential victim. The observed similarity pattern – like robbing like – results from differential exposure and from vulnerability. However, offenders can expect a higher ‘pay-off’ from less vulnerable targets, hence they may seek to increase their firepower by acquiring accomplices or deadly weapons. Such offenders are more likely to select relatively well-defended targets that have a relatively high pay-off.