45% of households does seem unusually high. Where'd you see the source article? I've been trying to find a copy and it's $37 to order one from the website.
Another look finds this page, Which shows that the ownership rates are based on BULLSHIT, in one link i found it said from phone surveys(as stated in the article they couldn't use these as they stopped in 2004) but had no further source of who did the survreys ect.... So after i looke dup the name of the report and googled it with the addtion of .pdf i found the full report and it says
", we calculated household firearm ownership rates
per state using the firearm suicide/total suicide ratio, which is
the proportion of all suicides in a state caused by firearms.11
This ratio has been highly correlated with firearm ownership
rates in the United States and other developed nations.12-17 There
are no direct data from 2007 through 2010 on firearm ownerships
rates in the United States; the last large state-based survey
of firearm ownership was performed in 2004 by the CDC’s
Behavioral Risk Factor Surveillance System."
https://www.procon.org/files/gunslawsanddeaths.pdf