US lumber prices are falling—fast.  On Tuesday, the price per thousand board feet fell $114 to $1,210, according to industry trade publication Fastmarkets Random Lengths. This comes after its record $122 decline last week. In all, the "cash" price of lumber is down 20%—the threshold in the securities world for a bear market—since the $1,515 all-time high set on May 28. What's driving the dip? Homebuilders and DIYers alike are finally balking at the exorbitant price of lumber. Indeed, new home construction in May is down 8.8% from the ...