Final answer:
Without an explicit statement from McArdle, we can infer that there is a likely need to shift resources to accommodate the increasing elder care demands due to the growing elderly population.
Step-by-step explanation:
According to the information provided, resource allocation in the next 20 years should consider the increases in the elderly population due to healthcare improvements and life expectancy rises. Nations are facing future scenarios where the elderly will form a much larger share of the population which will result in greater demand for elder care and shifts in social institutions. This would imply that resource allocation might need to focus more on the needs of the elderly. However, without a direct quote from McArdle, it's not possible to specify one of the provided options as the definitive answer. Nonetheless, the evidence suggests that there is a need for a transfer of resources to support the increasing care demands of the aging population.