Explanation:

- Statement 1 is incorrect: Population ageing is the process by which the share of the older population becomes proportionately greater, not lesser. This occurs due to declining fertility rates and increased life expectancy, leading to a higher proportion of elderly individuals within the total population.

- Statement 2 is correct: In most developed countries, the population in higher age groups has indeed increased. Factors include improved healthcare, higher living standards, and reduced birth rates, resulting in a growing proportion of older individuals.

- Thus, the correct answer is Option 2: 2 only, as statement 2 is the only correct statement.