Serious assaults and threats against Work and Income staff jumped 43 per cent in the two years before today's Ashburton killings.
The Ministry of Social Development said assaults and threats increased from 201 in 2011 to 247 in 2012 and 288 last year.
However, the increase was entirely accounted for by threats, which rose from 174 to 265 across the two years, while actual serious assaults fell slightly from 27 to 23.
The ministry said it typically posted one security guard at each Work and Income office, but 16 of its 157 offices had two guards and one site had three.
"From July 2007 to June 2012 there has been a net increase of six guards overall," it said.
"This is a result of 19 sites introducing a first guard, for example where an office is opening in a new area or, in some cases, second guard, while 13 sites have reduced the number of guards. Sites may have reduced the number of guards for a number of reasons such as the merger of two branches or the closure of offices."
The Ashburton tragedy this morning is by far the worst of a long series of attacks on Work and Income offices by angry beneficiaries. The roll-call includes:
November 1999: A man went berserk with a wooden club in the Orewa office, smashing six plate-glass windows, a computer and a sign, and sending staff scrambling for cover. No one was hurt. The man faced charges of intentional damage.
January 2001: A 33-year-old man drove a car through the front window of the Flaxmere office and attacked computers and furniture in what was said to be the worst attack on the agency up to that date. He was charged with five offences.
August 2002: A man used a bayonet and a taiaha to smash 20 computers at the Porirua office, telling staff to back away from their desks. The man, Michael Anstis, who was 28 at the time, was jailed for two and a half years for aggravated robbery and criminal damage.
November 2003: A 47-year-old man pulled a knife on staff at an office in Dixon St, Wellington. He was charged with assaulting a staff member, possession of an offensive weapon and damaging a computer.
February 2005: Two staff in the Hamilton East office were injured by a knife-wielding woman. A female employee was stabbed in the neck and shoulder and another worker was cut while trying to help. This incident prompted a major security review and security guards have since been posted outside all Work and Income offices.
September 2012: 59-year-old invalid beneficiary Sam Kuha smashed two windows at the Kaikohe office with a sledgehammer and went on hunger strike after being told he could not get an emergency food grant unless he saw a budgeter and waited three weeks for an appointment. He ended his hunger strike 30 days later when Social Development Minister Paula Bennett agreed to meet him. He agreed to pay a $480 bill for repairing the window and was convicted and discharged.