because retrenchment means losing their job and the alternative
(again suggested by you) is working for $1.5k per month?
you'll see it better if you were the sole breadwinner of your
family in your 40s with your wife waiting for food and children
wanting money for studies.
also, you should find out the number of people who were
retrenched vs the number of people who were fired for job
inefficiency
tl;dr: job insecurity has no correlation to job ability. (you
can be confident about your job too even if you dont know nuts)
Only abnormal people would be confident at their job when they
know nuts, but are you sure you want to degrade the discussion by
going there? 
You cannot be the sole breadwinner of the family if you are
earning only $1500, probably won't be able to keep anyone alive
until they are 40s.
Low income families usually would have both husband and wife
working to substain the family expenses, and nobody would earn only
enough to substain the family expenses as savings has and will
always be an important factor in a family.
There's no need to find out the figures for retrenchment and
work inefficiency, why would you need that figure for anyway? You
mean you need to prove to me that more people would be affected by
retrenchment and thus it is a common fear?
Like I have mentioned before, retrenchment is across the company
and the fear is not as bad being fired for work inefficiency.
People understands that retrenchment is beyond their control and is
not related to their work efficiency. But people's job seeking
confidence will be greatly affected if they were to be fired for
work inefficiency.
Perhaps you have already forgotten the real reason why you were
discussing about retrenchment and job inefficiency because you were
too focused on these two topics.
If you are talking about retrenchment, then let's imagine this
fear of retrenchment will exists in the hearts of every worker in
the company. But for some workers with job inefficiency issues,
they will have this job inefficiency fear on top of the common fear
of retrenchment.
Do you understand what I'm saying? 