at a minimum, I would consider (at least from a qualitative perspective) the current and prospective utilisation levels across one or more of the following dimensions:
- Housing (e.g. how many houses are currently present in the country, how many are currently being built and how many additional houses will need to be built in order to accommodate a 60% population growth);
- Infrastructure (e.g. how many schools, hospitals, public sector offices etc. are currently present in the country, at which capacity levels are they operating and how many will need to be developed to successfully deal with the increase in population). This dimension should also include any assessment connected to utilities-related infrastructure, as the increase in population will lead to increase consumption of electricity, water, etc. and therefore require investments in physical assets. Similar considerations may apply to other elements such as roads, train stations, airports and so on;
- Public sector workforce (e.g. as above, based on an assessment of the current capacity level, I would try to determine how many additional public sector employees will be needed to face the increase in demand).
The above list is by no means complete and could be further expanded as needed, however, given the generic nature of the question, I would start from those considerations and then move to other areas as needed.
For all of the above, you should also determine a list of priorities, the required time frames, the associated cost of each investment and how the Government is going to finance that cost in order to decide what makes more sense.
I hope this is helpful. Let me know if you have any doubts.