Someone who was 7 during Katrina at that time is roughly 28 today.
Using the Census ACS age brackets, about 20-ish% of louisiana's population is under 15, and another 20 is between 15 and 29. Everyone 30 and older adds up to the other 60.
So a hair over 60% are were at least 7.
But that's who lives there now not who lived there then. Between 2005 and 2006 the state population dropped by 6% and most of that displaced population never returned - people coming in from elsewhere weren't there for Katrina. So the fraction who were both living there AND old enough to remember it is considerably smaller than 60%.
Claiming 9 year olds don't remember Katrina is quite an abuse of the word "roughly". The percentage of Louisiana's population under 25 is 33%, we can agree they don't "remember". Anything else requires considerable stretching with a hand-waving accompaniment. I can do that part just as well as any other internet person. Let's see, how about the fact that what followed Katrina was years of rebuilding? Someone from New Orleans probably saw its aftermath around them for 4-5 years.
Why are you assuming the rapid increase in LA’s population from 2006 to 2010 did not have a significant portion of temporarily displaced people moving back?
Oh, then you’re of course aware that many many people did in fact return, and that your earlier estimate of the number of people coming to LA after 2005 that hadn’t lived there before was over-estimated.
Using the Census ACS age brackets, about 20-ish% of louisiana's population is under 15, and another 20 is between 15 and 29. Everyone 30 and older adds up to the other 60.
So a hair over 60% are were at least 7.
But that's who lives there now not who lived there then. Between 2005 and 2006 the state population dropped by 6% and most of that displaced population never returned - people coming in from elsewhere weren't there for Katrina. So the fraction who were both living there AND old enough to remember it is considerably smaller than 60%.
So like I said, roughly half.