Gareth Kiernan​, chief forecaster at Infometrics, says household costs could increase by $42 a week if forecasts for higher inflation come true, Stuff reports. According to Kiernan, with typical weekly household expenditure sitting at about $1393, a 3% lift in inflation over the next year would add nearly $42 to the average household weekly running costs. Kiernan also noted the rise in inflation was driven by global issues which were beyond the control of the Reserve Bank.