While geopolitical tensions in the Middle East caused a sharp rate spike in March, the gradual erosion of the sub-4% mortgage share suggests that major life events — jobs, kids and divorces — are slowly forcing movement in an undersupplied market.Builder incentives: New construction inventory continues to bridge the gap, with builders offering rate buydowns to keep the 4% to 6% bracket viable for new entrants.The 6% club is growing: The share of homeowners with mortgage rates of 6% or higher reached 21.9% i ...