NEW YORK: Over the first six months of the year, some 200 million barrels of oil have gone missing.

Or perhaps not they are not missing, but have simply been quietly put into storage outside of the world’s developed economies.

Or perhaps these barrels never existed in the first place but are only the product of underestimated demand for oil or a too-optimistic view of how much crude the world is producing.

For a long time, the International Energy Agency’s Monthly Oil Market report’s “miscellaneous to balance” item — a catch-all that covers stock changes in non-OECD countries and noise in the data-- was showing a modest deficit.

But the latest report now plugs in a miscellaneous surplus of 1.6 million barrels per day in the first quarter and 0.6 million bpd in the second quarter to balance its global supply and demand estimates.

While a bit smaller than the balancing item assumed in the August report, these miscellaneous items represent considerable uncertainty for oil forecasters.

If demand is stronger than current estimates then the oil market is running much hotter, with much less spare production capacity than currently thought.

But if a lot of this oil is going into storage tanks, particularly strategic storage, then perhaps the balance is more comfortable than thought.

What is significant now, is that the miscellaneous items are now larger than the reported commercial stock changes reported in the developed world in the first two quarters of the year (0.4 million bpd and 0.5 million bpd).

Moreover, the miscellaneous item is getting uncomfortably large when compared with quarterly demand growth.

The shift in the miscellaneous item, described as “nothing short of dramatic,” by IEA analysts in a thoughtful piece leading this month’s Oil Market Report, stems from trends that are reshaping the oil market.

The emergence of China, India and other large non-Western economies as major oil consumers in their own right has diminished the value of traditional market data centered on the nations of the Organization for Economic Cooperation and Development.

Previous episodes of “missing barrels,” such as in 2006, have largely turned out to be rooted in the difficulty in estimating demand growth in these countries.

What at first seemed like oil disappearing into unknown storage tanks later turned out to be rampant consumption growth.

That set the stage for the surge in crude prices as the market adjusted to much stronger demand.

But with evidence aplenty of a slowdown in economic activity in the developing world, particularly in China, perhaps this time these missing barrels are going into storage tanks.

The IEA itself takes a stab at investigating these issues, noting that Chinese commercial oil inventories are now 21 million barrels higher than a year ago.

Yet the implied stock change in China — the sum of reported refinery runs, net imports and production data — suggests that country’s inventories should be a staggering 104 million barrels above year ago levels.

The conclusion is that China added a staggering 80 million barrels of oil to its strategic reserves over the 12 months between June 2011 and 2012.

If so, China may have already filled at least half of the second phase of its strategic petroleum reserves.

On a 12 month basis, that sort of stockpiling would be some 220,000 barrels per day, about a quarter of the current estimate for annual global demand growth.

That could prove a nasty surprise for oil bulls, if true. After all, China’s SPR may well be filled by the summer of 2013 if these estimates are correct.

That would, presumably lead to a reduction in Chinese crude oil purchases in the second half of 2013.

But with little clear data, it is hard to say conclusively how much of this oil is ending up in strategic stocks.

That’s the heart of the problem for oil analysts. Is this latest missing barrel episode bullish or bearish?

Even if China’s strategic stockpiling only began in earnest this year, it cannot account for even half of the 200 million barrel missing barrel figure.

Nor does adding in Iran’s need to resort to floating storage to deal with periodic episodes of unsold crude oil give us a complete answer.

The size of the miscellaneous item suggests that there has to be some unaccounted-for demand or an overestimate of supply.

Oil storage facilities do not spring up overnight.

With time and more data, the IEA will likely trim back this balancing item. But for traders looking for signals where the market is heading, it will add a new element of uncertainty to their calculations.

— Robert Campbell is a Reuters market analyst. The views expressed are his own.