ANZ Bank and government-owned Kiwibank were the clear market share winners in mortgages through 2013.
ANZ's mortgage book grew by $3.92 billion to nearly $57.88 billion in the calendar year, lifting its share of the market to just over 31 percent, up from 30.7 percent a year earlier.
Every percentage point change is worth more than $1.8 billion.
Kiwibank's mortgages grew by $1.04 billion to $13.12 billion, taking its market share to just over 7 percent from a little below 7 percent a year earlier.
ANZ and Kiwibank's gains were largely at the expense of the Bank of New Zealand, which is owned by National Australia Bank, although its mortgage book also enjoyed strong growth.
BNZ's book grew slightly more than Kiwibank's but, because it's a much larger bank with a mortgage book of $29.6 billion, its market share fell to below 15.9 percent from nearly 16.25 percent.
Contributing to BNZ's slower growth was the fact it had been lending a great deal to people with small deposits ahead of the Reserve Bank's rule limiting such lending to no more than 10 percent of each bank's new mortgage lending.
That rule came into force from October.
ASB Bank, which is owned by the Commonwealth Bank of Australia, managed to grow its market share despite having an even greater exposure than BNZ to lending to people with small deposits.
ASB is the second-largest home lender in New Zealand, behind ANZ, with a mortgage book of $41.23 billion.