https://www.rba.gov.au/speeches/2019/sp-gov-2019-10-29.html  12/18  10/30/2019  Some Echoes of Melville | Speeches | RBA  Graph 9  Slower population growth means there is less need to add to the capital stock to accommodate more people. Less home and other building is required, and there is less need to invest in infrastructure to meet the needs of a growing population.
While there are some specific areas where more investment might be needed, the overall effect of lower population growth is to reduce investment. A third explanation for lower investment demand is that people are less optimistic about future economic growth.