The forecast for the net earned premium of mortgage insurer Genworth has been cut by A$40 million, and may be between 17 per cent and 19 per cent lower over the full year to December 2017, the company said on Friday, with only a few weeks left in its financial year.The revised estimate on the decline in net earned premium compares with a fall of between ten per cent and 15 per cent outlined in recent months.Genworth said it expected its full year loss ratio to remain in a range from 35 per cent to 40 per cent.Assessments by actuaries and "independent reviewers" have led Genworth to review its premium earnings pattern, the company explained in a release via the ASX.Two factors of note, Genworth said, were:-- "losses from mining regions … continuing to occur at late durations"; and-- "improvements in underwriting quality in responses to regulatory actions … extend the average time to first delinquency."Genworth made no references in this trading update to the loss of business to Arch Capital Group and captive insurers.The equity research house Morningstar on Friday estimated the net profit for Genworth over 2017 would be $169 million, 20 per cent less than in 2016. The NPAT for this once dominant force in lenders mortgage insurance may "stabilise at around $150 million" over the four years to 2022, Morningstar said.