Data: The Conference Board and The Business Council; Note: A number below 50 reflects more negative than positive responses; Chart: Emily Peck/Axios The CEOs of the world's biggest companies lost confidence in the economy this month as the Iran war dragged on, a new survey finds. Why it matters: Business leaders who lack confidence tend to pull back on hiring and investment, weighing further on the economy. Zoom in: CEO confidence fell 12 points in the second quarter of the year to 47, per the survey from The Conference Board, a nonpartisan think tank, and The Business Council, an association of CEOs. Any number below 50 signals negative sentiment. 141 Fortune Global 500 chief executives participated in the survey, conducted from May 4 to May 18, the war's third month. Zoom out: When President Trump first took office last year, CEO confidence shot up to its highest levels in years on hopes that he would take a light touch with regulation and pass a big, juicy tax cut.…