How long can strength in China's commodity imports co-exist with weakness in other key indicators, such as manufacturing?

If you accept the argument that China can't continue to import record, or near-record, levels of major commodities while experiencing slowing growth, then one of two outcomes becomes inevitable.

Either commodity imports start to moderate to align more closely with other economic data, such as the HSBC Purchasing Managers' Index, which fell for a fourth straight month in April, or China's growth shows evidence of re-accelerating.

So far this year, strength in commodity imports has tended be put down to either one-off factors, or demand unrelated to actual consumption, for example, buying iron ore in order to secure financing to use in unrelated investments.

If these factors are the reason behind the seeming disconnect between natural resource imports and the overall economy, then the most likely outcome will be for imports of crude oil, iron ore, copper, soybeans and other commodities to ease in coming months.

Crude oil imports jumped 22 percent in April from March to 27.88 million tonnes, equivalent to 6.78 million barrels per day (bpd), which exceeds the prior record high of 6.65 million bpd in January.

The strength in crude imports comes amid slowing oil demand, with a calculation of implied consumption coming out at 9.96 million bpd in the first quarter, a decline of 0.6 percent from the same period a year earlier.

April's record oil imports also came amid maintenance at several refineries, which normally trims demand.

The most likely explanation is that China has been adding to commercial stockpiles, and the start up of two new refineries certainly supports this view.

However, the extent of the strength in crude imports suggests that strategic stockpiles are also being filled, although this cannot be known for certain as this information isn't disclosed.

PRICE A FACTOR FOR IRON ORE, COPPER

Iron ore imports were the second highest on record in April at 83.89 million tonnes, and the first four months of the year has seen a jump of 21 percent from the same period in 2013.

While some of April's strength could be put down to higher steel production, it also appears likely that some of the imports were related to shadow financing deals, even though anecdotal reports suggest the authorities are making it harder for traders to use commodity imports as collateral for credit.

It may be that April represents the peak of imports for credit purposes, implying that iron ore shipments may slow in the next few months, or at least become more linked to steel output.

The other factor with iron ore is that weaker prices tend to boost imports, irrespective of the state of steel demand.

Spot iron ore hit $104.70 a tonne, the lowest so far this year, on March 11, just around the time many cargoes for April delivery would have been booked.

Cheaper prices may also help explain the 7.2 percent gain in copper imports to 450,000 tonnes in April from the previous month.

London copper dropped to its closing low for the year on March 13, making it attractive for Chinese traders to import the industrial metal.

China's State Reserves Bureau, the official stockpiler, was also buying in April, which helped support local premiums and thereby boosting the appeal of imports, Zhou Jibe, dealer and senior analyst at China International Futures (Shanghai) Co Ltd, told Reuters.

Looking at the major commodity imports and it seems that imports haven't been driven by strength in actual consumption, with stockpiling boosting crude and copper, and shadow financing doing the same for iron ore.

Whether strategic stockpiling continues apace is in the realm of speculation, but it does seem likely that the boost to commodity imports for financing deals will be lower in the next few months.

However, if the Chinese economy does start to pick up slightly, some real demand for commodities may offset any decline from stockpiling and financing.