The S&P 500 index in the US has increased for four consecutive weeks, rebounding strongly from the weakness in March. That leaves it up 13 per cent from the recent lows, and almost three per cent above its pre-conflict peak. You could be forgiven for wondering why the sharemarket is hitting new records, with oil prices still very high and the situation in the Middle East unresolved. There’s never just one reason why markets move up or down, but right now the answer could be a simple one.