Why do negative population growth cause problems for countries?
This is a somewhat vague question as there are possibly many
ways negative population growth can affect the people, if
considered in a closed system such as a continent, race, or
globally negative population growth will ultimately lead to no
people :D
If i don't stretch your question i'll assume by "the people" you
mean the people in the population. I make this distinction because
there are many populations of people apart from each other, for
example the population of one city compared to the population of
another. A state population, country population, continent, or
global population. Perhaps even a race population.
But with my prior assumption that "the people" refers to the
people in a specific population, i would think that a negative
population growth rate would effect it's people in a number of
ways, ranging from efforts made to identify the cause of negative
population growth to efforts in attending to these causes as to
prevent the population from reaching too few in number to sustain
itself.
I realize this answer is vague, but i think your question needs
some reworking if you are looking for a specific answer.
Negative population growth in a region that is considered
"overpopulated" might positively effect the people, and vice versa
in the case where a population is already dwindling to a number
that would be considered threatening to the continued existence of
a population.
If we look at the global population, throughout our history
there are examples and obstacles that have lead to the growth of
population, and cities and countries are somewhat measured in
greatness by their population so in those terms a growing
population would be considered healthy or prosperous whereas a
negative population growth would be indicative of a country or
society that is doing poorly.
I think its important to emphasize the population growth rate is
a measure of population growth divided by a time period. This is
different from an overall population. That being said the effects
of a negative population growth rate are somewhat dependent on the
overall population at a specific time.