In the 1952 paper of Hans Singer from which I have already quoted,
one of the conclusions that Singer emphasis is the need to raise the then existing rate of saving.
He argued,
with some assumptions about production conditions,
that to achieve even a 2% rate of per capital growth,
with a population growing at 25% per year,
a rate of net savings of 6% is necessary,
and that this rate of saving is about three times the rate actually observed in underdeveloped countries (Singer, 1952, pp.397-8).
The current average rate of saving is no longer a third of that figure,
but substantially higher than the figure.
The weighted average ratio of gross domestic saving for low income developing countries is estimated to be about 22%,
and that for middle income developing countries about 25%;
and, even after deducting for depreciation, Singer's target has certainly been exceeded.
And, even with a faster growth of population than Singer anticipated,
the weighted average of GDP growth rates per capital has been about 2% per year for low income countries
and more than 3% per year for middle income countries over the seventies.