Read the following passage and answer the item that follows. Your answer to this item should be based on the passage only.

Commentators have attributed a recent spike in global edible-oil prices to a mix of causes: poor harvests in major oilseed-producing regions, higher shipping costs, and export restrictions imposed by some producing countries to protect domestic supply. Increasing attention has also turned to rapidly rising demand from populous, fast-growing economies, where rising incomes are shifting diets toward more oil-intensive processed and fried foods, a shift some analysts believe could tip global supply into a sustained shortage.

With reference to the above passage, the following assumptions have been made:

1. Export restrictions are the single largest cause of the recent price spike.

2. The sustained shortage some analysts foresee is now certain to occur.

Which of the above assumptions is/are valid?