Not to mention the Scouse diaspora from the 70's and 80's living down south.
The population of the city of Liverpool is quite a bit lower than the 1970's, I'll grant you. The population of Merseyside or the newly formed Liverpool City Region is not significantly much lower than it would have been if those entities had existed in the 1950's/60's. Contrary to myth, not everybody moved down south or emigrated to Canada. Lots of people moved a few miles outside the city limits.