OTTAWA, Ont. — A boost from price increases for petroleum products and primary metals was not enough to keep manufacturing shipments from declining in April, losing most of March’s gains, Statistics Canada reports.

This was the third decline so far in 2006, and followed March’s 1.6% advance in shipments.

A substantial drop in the production of aerospace products and parts was largely behind April’s 1.5% decrease in shipments which stood at $50.4 billion. Excluding the aerospace industry, shipments were down a more modest 0.4%.

Quebec and Alberta were among the seven provinces and the Yukon to post lower shipments in April. Big declines in aerospace production coupled with the food and wood products industries pulled down shipments in Quebec by $393 million (-3.1%) to $12.1 billion.

The sharp drop in shipments boosted the inventory-to-shipment ratio to 1.31 in April, equal to the ratio’s recent high set in February.

“Uncertainty in the manufacturing sector, due in part to the strengthened value of the Canadian dollar and soaring input costs, have contributed to some weakness in shipment activity. As a result, the trend of the inventory-to-shipment ratio has been on a gradual, upward movement over the last few months,” Statistics Canada commented with the release of the data.

The inventory-to-shipment ratio is a key measure of the time, in months, that would be required to exhaust inventories if shipments were to remain at their current level.