sydneyshares of nib holdings ltd slid monday after its headline firsthalf earnings missed consensus with lower margins in its flagship division the stock was down almost 12 at 700 australian dollars and is currently the worst performer on the asx 200 after earlier hitting a threemonth low of a688 nib shares are down around 94 so far this year the australian health insurer said monday that net profit after tax including discontinued operations was up 13 at a916 million us632 million for the six months to december after benefiting from an improvement in net investment income ubs said in a note that the companys npat came in ahead of its estimate of a89 million but below consensus expectations of a97 million nibs flagship unit australian residents health insurance saw its margins reduced in the first half compared to the previous year the units margins also missed ubs and consensus expectations nib chief executive mark fitzgibbon warned that while market and business conditions look favorable for the companys strategy challenges remain inflation rising interest rates and slowing economic growth suggest some level of caution is required claims are still lower than wed expected and at some point volumes will lift he said