Countries undergoing a simultaneous population reduction and increased percentage of retirees between now and the year 2050 will likely need more immigrants.
Step-by-step explanation:
If the nation's population is decreasing, while number of retirees are increasing then such scenario showcase that the nation is contain with more old age or senior citizen human beings as compared to youth or adult citizens.
Thus the immediate solution for rectifying such issues is to adapt the immigrants and allow some law amendments in most appropriate way possible to accept them without inviting any further conflict or war. The long term process can be asked from citizens to expand their family by providing sufficient medical and other required facilities in states to them in order to avoid mortality rate.