The bottom line earnings of Genworth - the country's largest mortgage insurer - almost halved last year as the impact of accounting changes, mandates lost since 2015 and the regulatory crackdown on high LVR lending crunched the company's revenue line.Genworth suffered a 49 per cent slide in profit to A$75.7 million for the 12 months to the end of December.Underpinning the result was a 24 per cent fall in net earned premium, which had been previously flagged to the market by managing director, Georgette Nicholas."Our full year financial performance is in line with our guidance and our expectation of a transitionary year for Genworth," Nicholas said.While the big fall in profit was partly due to the decline in high LVR lending by banks and the softening housing market, it was mostly attributable to accounting changes that require Genworth to delay recognition of premium as revenue.Nicholas said the company's net profit would have declined by only around six per cent on the 2017 bottom line of $149 million if the accounting adjustment had not impacted the result.The company's net earned premium should begin to recover in 2019 under the new accounting policy but it is not guaranteed given the possibility that lenders could cancel insurance arrangements with the company.Genworth is heavily exposed to its partnership with Commonwealth Bank, which is believed to account for up to 45 per cent of all LMI policies underwritten by the company.The contract with CBA expires at the end of 2019, which means Nicholas is under pressure to ensure that the arrangement is renewed.Another factor weighing on Genworth is the uncertainty surrounding the future of mortgage broker remuneration following the release of the final recommendations of the Hayne Inquiry.NAB uses Genworth LMI for loans originated through its proprietary broker platforms - FAST and PLAN. This business accounts for around 10 per cent of Genworth's LMI book.The share prices of ASX-listed broker networks have plummeted by almost 30 per cent this week amid fears that brokers will struggle to retain customers without commissions from lenders.Although Genworth remains the largest provider of lender's mortgage insurance in Australia, it is trying to diversify its revenue sources to counter headwinds eroding its core business.Westpac's move in 2015 to insource its LMI functions with the backing of Bermudan-based reinsurer Arch Capital was a critical blow that forced Genworth to review its business model.The company recently launched a bespoke risk management product through a Bermudan vehicle that provides complementary risk tools to traditional LMI cover.It has also entered new excess of loss insurance agreements with Australia's five largest banks.Genworth's ASX-listed scrip closed up nine cents or 4 per cent to $2.35.