Dow Jones Indexes today explained that a system problem beginning at 13:50 ET yesterday amid unusually heavy volume caused the 70-minute lag in correctly calculating the value of the Dow Jones Industrial Average (DJIA) and the subsequent downward spike in the reported index value when the problem was corrected at 15:00 ET.

Michael A. Petronella, president, Dow Jones Indexes, said the problem arose in the system responsible for feeding market data into the calculation system. While the DJIA was still being calculated and disseminated, the calculator was not receiving the underlying component prices of the DJIA on a timely basis. Once the slow data feed problem was recognized, Dow Jones Indexes switched to a redundant market data system. This switch-over caused prices that were received during the latency period to be processed all at once, bringing the index immediately in line with its underlying component stocks.

Petronella said all Dow Jones Indexes systems are fully redundant, which enabled it to move to another system with timely pricing. Dow Jones Indexes is continuing to investigate the latency issue to correct the root cause of the problem. Dow Jones Indexes expects normal operation of the DJIA today using its redundant market data system.