WASHINGTON — Defense Department spending remained relatively flat in the fourth quarter of 2015 compared with a year earlier, according to data released Wednesday by the US Treasury Department.

Overall Pentagon outlays (Operations & Management plus Investment) during October, November and December 2015 were $100.1 billion, 1 percent lower than a year earlier. Army Investment (Procurement plus Research, Development, Test & Evaluation) spending dropped by 9 percent to $6.3 billion, while Air Force Investment gained 5 percent to $16.7 billion. Navy Investment remained flat, dropping $100 million to $14.3 billion.

Byron Callan, an analyst at Capital Alpha Partners, also calculated what he describes as the market outlays, defined as Investment spending plus 35 percent of O&M. The market percentage changes for the services closely mirrored the Investment changes: down 9 percent for Army; up 4 percent for Air Force; flat for the Navy.

These figures don't offer a complete picture of the defense industry, he cautioned in a note to investors, because they don't include firms' commercial or international sales. They also don't reflect acquisitions and divestitures, which affect Wall Street's view of defense stocks.

"That all said, our work suggests a decent correlation between the direction (plus or minus) of organic US defense sales comparisons and the direction of DoD investment and O&M outlays," he wrote. Consensus sales data "suggests to us that there should not be material positive or negative surprises as far as Q4 DoD-related sales are concerned."

Twitter: @andclev