>

This is adjusted for death.  Surviving children per women.
I kick start deaths from the age of their 40s -and Im quite brutal insofar as Im basing only 60% reaching that, 70% for the generation after.
What am I missing here?

That historical records and community estimates are based on hand counted censuses whereas your analysis is based on a lot of mathematical assumptions that didn’t actually happen. >

Are you arguing that your estimates are better than census records? >

The British census data only includes Irish-born.
426,000 were irish-born in 1901, fifty years after the Famine.  The 2 million is an estimate.
But that doesn't include an unspecified number of second and third generations.
The historians and demographers come up with 2 million, but two cohorts born over a century (based on number of children born per women) would suggest 3x time as many offspring. >

You're assuming they stay in Britain instead of say, migrating to America or elsewhere >

You're missing death. People die. Children died especially often. Your model assumes that all children survive to adulthood, which is not the case.