I can't quite understand the difference here between the crime classes. Burglary (the victim is absent) and robbery (the victim is present) are somehow separate from theft?

Theft is taking off with something that is in plain view. Burglary includes breaking in, and robbery involves violent force. Lawgivers the world over especially detest violence, so no surprise that the latter two traditionally attract stiffer penalties.

"Cat burglary" isn't a violent crime, though.

Theft is illegally depriving someone of something. Burglary includes an unlawful entry component.

There's a glossary here: https://www.justice.govt.nz/justice-sector-policy/research-d...

In short:

Burglary: Entering a building intending to commit a crime.

Robbery: Stealing/attempting to steal from someone by force (or threatening force).

Theft: The actual stealing of stuff.

Burglary is breaking and entering with intent to commit a crime. There is nothing specific about theft or the presence of the victim in burglary.

When did NZ stop using lead in gas?

Banned in 1996, same as the USA. I'm not sure how heavily it was phased out before then. Certainly newer vehicles were already using unleaded petrol at the time.

Everyone's probably on their mobile phones and FB.

It really does drop as Facebook grew. Make of that what you will.