What is the central theme in Angela's Ashes and how is it developed in the story?

One of the main themes of this story that cannot be
ignored is that of poverty. The poverty in which the McCourt family lives is shown to be
brutal, unyielding and pervasive. It is clear that in Limerick, poverty is accepted and
part of everyday living. Note the way that the dole system that is set up is never shown
to be enough to give them sufficient food and shelter. The systems that exist seem to do
nothing to combat the root causes of poverty, and are often extremely humiliating, such
as when Angela goes for assistance at the Dispensary and is insulted and made fun of by
those in charge, saying that her husband has an "English
tart":

Well,
we know why, don't we? We know what the men of Ireland are up to in England. We know
there's the occasional Limerickman seen trotting around with a Piccadilly tart, don't
we?

Again and again,
reference is made to the small amount of money that the dole gives the McCourts, and at
the start, when they receive nineteen shillings a week for going on the dole, Angela
poignantly and bitterly remarks that it is "just enough for all of us to starve
on."

However, equal focus is also given to the terrible
living conditions that the McCourts are forced to endure. In their final house before
they are evicted, the lavatory for eleven families is right outside their door and the
rain makes the downstairs room uninhabitable for half of the year and the family retire
upstairs to the bedroom. It is clear that the deaths of the twins are largely a result
of living conditions and their hunger.

We see the McCourt
family in a downward spiral of poverty, which worsens as Malachy goes to England
supposedly to get work but only spends the money he earns on his alcoholism. The nadir
of this descending spiral of poverty occurs when Frankie sees his mother begging at the
priest's house for food for her family, sacrificing any decency and social standing in
order to gain something that she can use to feed her children. Throughout it all, Angela
shows considerable determination and grit in her willingness to humiliate herself and
receive humiliation in order to look after her family.