Blackstone Group LP reported an increase in third-quarter profit Thursday as continuing market strength buoyed the value of its investments. Net income for the quarter climbed to $442.7 million, or 64 cents a share, from $377.9 million, or 55 cents a share, a year earlier. The value of Blackstone's private-equity portfolio climbed by 7.5% in the quarter, a slowdown from the 9.5% growth it posted in the second quarter but significantly outpacing its growth in the third quarter of 2017.