For more than a year, food manufacturers have been shaving package sizes and raising prices, declaring that they had little choice because of unprecedented increases in the cost of raw ingredients like corn, soybeans and wheat.

Now, with the price of grains and other commodities plunging, it may seem logical that grocery prices will follow. But while prices for some items like milk and fresh produce are dropping, those of most packaged items and meat are holding firm or even increasing. Experts warn that consumers should not expect lower prices anytime soon on most items at the grocery store or in restaurants.

Government and industry economists project that the overall cost of food will continue to climb in 2009, led by increases for meat and poultry. A big reason, they say, is that food companies still have not caught up with the prolonged run-up in commodity prices, which remain above historical averages despite coming down from their highs early this year.

The Agriculture Department is forecasting that food prices will increase 3.5 to 4.5 percent in 2009, compared with an estimated 5 to 6 percent increase by the end of this year.

Some economists project even steeper increases next year. For instance, Bill Lapp, principal at Advanced Economic Solutions in Omaha, said he expected food prices to jump 7 to 9 percent next year.

“For the last 21 months, food manufacturers, restaurants and livestock producers have been absorbing significant costs that in my view are likely to be passed on to consumers in 2009 and beyond,” said Mr. Lapp, a former chief economist at ConAgra Foods.

While predicting future food prices is an inexact science, data released by the Labor Department last week suggested the forecasters might be right.

Overall consumer prices recorded the biggest drop in the history of the Consumer Price Index, but food prices continued to inch upward, albeit at a slower pace than in previous months. The C.P.I. showed that grocery prices rose 0.1 percent in October.

Some of the more visible items on grocery shelves, including produce and dairy products, dropped sharply in recent weeks, but not enough to offset the general trend of rising prices. Restaurant prices rose 0.5 percent in October.

Commodity prices began climbing rapidly in the fall of 2007, and food companies were hit hard by the increases. They tried to slow eroding profit margins by cutting operating costs, making packages smaller and raising prices.

Some companies, like Kellogg and Heinz, have managed to offset the higher ingredient costs and post robust profits by using shrewd commodity hedges and by raising prices without losing many customers. They also benefited from a trend of consumers eating out less and buying more groceries.

But other food companies have struggled. Hershey, for instance, locked in high cocoa prices this year only to see prices drop this fall, analysts say. And meat and poultry companies have been hit by higher feed costs and a limited ability to charge higher prices, at least in the short term.

Now, even though costs for ingredients like corn and wheat have dropped, meat and poultry providers say they still have not raised prices enough to cover their increased costs. And packaged food manufacturers are unlikely to lower prices because commodity costs remain relatively high and they are still trying to rebuild eroded margins.

Michael Mitchell, a spokesman for Kraft Foods, said that the company’s food ingredient costs this year were running $2 billion higher than in 2007, a 13 percent increase, but that the company had raised its overall prices by only 7 percent.

William P. Roenigk, senior vice president and chief economist for the National Chicken Council, said his industry had been losing money for more than a year. Chicken producers are now trying to recover those costs by reducing production, which will eventually alter the balance between supply and demand. “The time is coming when we’re going to see a very significant increase in the retail price of chicken,” he said.

The restaurant industry, which has been battered by a sharp drop in customers, also says it has not been able to raise prices enough to keep pace with the cost of ingredients.

People in the restaurant business said they did not like raising prices during an economic downturn. “If anything in this environment, one would be looking at the ability to offer much greater emphasis on value pricing in restaurant menus,” said Hudson Riehle, chief economist of the National Restaurant Association. “In contrast, exactly the opposite is happening. Our operators are being forced to raise menu prices at the highest rate since 1990.”

Predictions about food prices are subject to change because commodity prices are unpredictable. Ephraim Leibtag, an economist for the Agriculture Department, said food inflation would slow by the middle of next year if commodity prices remained low. “Right now the forecast is about 4 percent, but that would be lowered if we do not see any surge in commodity costs over the next few months,” he said.

A reason that overall food prices are expected to continue increasing is the lag between price increases for basic commodities and for finished food products in the grocery store, particularly for meat and processed foods. Consider the price of corn, an ingredient in things like cereal and breaded shrimp. It was not too long ago that corn hovered around $2 or $3 a bushel.

But corn prices began climbing last fall and peaked around $8 a bushel in June. They have since dropped to about $3.50 a bushel, still above the historical norm. Some food manufacturers locked in prices for corn and other commodities in the spring and summer, fearing that prices could go even higher. But prices fell instead, and they are now stuck with the higher prices until their contracts expire.

When costs go up for livestock producers, they are often unable to immediately raise prices because those prices are set on the open market, which is dictated by supply and demand. Instead, they begin reducing the size of their herds or flocks, which eventually leads to less meat on the market and higher prices. But reducing livestock production can take months to years, and in the interim it can actually suppress prices as breeding animals are slaughtered to reduce production.

The prospect of more food inflation is inflaming a debate over its causes. Many food manufacturers and economists maintain that one culprit is government policies promoting the use of ethanol fuel made from corn.

About a third of the corn crop is used for ethanol, putting ethanol producers in competition with livestock farmers and food manufacturers. The result, they contend, is that prices for corn are now higher and more volatile.

“The connection of oil prices to agricultural commodities is new as of 2007, and it’s a major game changer for those in the food production business,” said Thomas E. Elam, president of FarmEcon, a consulting firm.

But ethanol advocates counter that the food industry’s arguments have been proved false, saying that corn prices have declined as ethanol production is increasing. Matt Hartwig, spokesman for the Renewable Fuels Association, an ethanol industry group, said food companies were “very quick to tell the American public that they had to raise food prices because corn was so expensive, and that the reason corn was so expensive was corn-based ethanol.”

Mr. Hartwig added: “Now, clearly, we know that relationship doesn’t exist. If ethanol isn’t the reason, what is the real reason for food prices going up?”

一年多以来，食品制造商宣称，由于玉米、大豆和小麦等原料价格空前上涨，他们几乎没有选择，唯有削减包装尺寸，抬高价格。

现在，随着谷物和其他消费品价格的飞跃上升，食品价格跟着上涨似乎大有可能。尽管有些东西如牛奶和水产品的价格正在下降，但大部分的包装物和肉类的价格依然坚挺甚至还在上升。有专家警告说，消费者任何时候都不要奢望在杂货店或饭店里的消费会很快地有所下降。

政府和产业经济学家预言，食品总成本在2009年会继续爬升，肉和禽类更为领先。他们说，一个最大的原因就是，尽管曾从年初的高价位跌落，食品企业仍然没有追赶上初级商品价格长时间的升高，还保留在历史平均数之上。

农业部门预测，与估计的截至今年年底的5-6%的价格上涨相比较，2009年食品价格将上涨3.5-4.5%。

还有一些经济学家预测，明年上涨的幅度甚至更大。比如，Bill Lapp，奥马哈高级经济研究所的负责人就说，他预计明年食品价格会上升7-9%。

还有一些经济学家预测，明年上涨的幅度甚至更大。比如，Bill Lapp，奥马哈高级经济研究所的负责人就说，他预计明年食品价格会上升7-9%。

尽管预报未来食品价格是一门不精确的学问，但劳工部上周公布的资料却暗示预测可能是准确的。

所有零售价格都记载了消费物价指数历史上的最大下跌幅度，但食品价格却继续步步见涨，虽然在先前的几个月中速度有所减缓。

杂货店货架上更多可见的商品，包括农产品和乳制品，在最近几周价格跌得很厉害，但不足以抵消价格升高的总体趋势。10月份，饭店的价格就提高了0.5%。

农产品价格在2007年秋季开始升得很快，食品企业受到此次物价上涨的严重打击。他们设法通过裁减运营成本、改小包装和提高价格来慢慢蚕食利润空间。

有些企业，象家乐氏和亨氏，通过运用精明的农产品限制和提高价格来设法抵消越来越高的配料成本和稳定强劲的利润，同时又不致丧失大量的消费者。他们也受益于这一趋势——消费者外出就餐日益减少而购买更多的食品。

可是另外的食品企业却在挣扎。分析家说，例如好时公司，巧克力价格居高不下，只有在这个秋季才看到有所下调。肉类和禽类企业因饲料成本越来越高、至少在短期内调高价格能力有限而倍受打击。

现在，即使诸如玉米和小麦之类的农作物成本下跌，肉类和禽类供应商也会说他们依然没有把价格提高至足以将他们增加了的成本包含在内。包装食品制造商未必会降低价格，因为农产品成本依然比较高，他们依旧想方设法重建越来越小的利润空间。

卡夫食品发言人Michael Mitchell称，该公司食品配料成本今年比2007年多花了20亿美元，增加了13%，但公司全部商品价格只提高了7%。

William P. Roenigk，全国鸡肉理事会的高级副会长和首席经济学家反映，他的工厂亏损已一年多了。鸡肉生产商现在正试图通过减产来弥补成本费用，这将最终改变供需平衡。“我们将看到鸡肉零售价猛升的时刻正在到来。”他说。

由于顾客锐减而被弄垮的餐饮业也说，他们不可能将价格充分提高以跟上材料成本。

餐饮行业人士说他们也不愿意在经济低迷时期拉高价格。“如果这种环境下能做什么的话，那一定是着眼于大力强调餐厅菜单价值定价的能力。”美国国家餐馆协会首席经济学家Hudson Riehle说。“相反，现在发生的情况却恰恰相反。我们的经营者正被迫进行自1990年以来最大幅度的提价。”

预言食品价格将改变是因为物价不可预知。Ephraim Leibtag，农业部门的一位经济学家说，如果物价维持在低水平的话，食品通胀到明年年中会减缓。“现在预测为大约4%，但假如往后几个月看不到物价飙升，那有可能会低一点。”

预期所有食品价格继续上涨的一个原因就是，基本商品和杂货店里食品成品价格上涨之间的滞后，尤其是肉和加工过的食品。仔细看看玉米，麦片粥和沾滚过面包屑的小虾之类的配料就知道了。不久前玉米价格还徘徊在2-3美元一蒲式耳呢。

不过玉米价格去年秋天就开始攀升了，6月更是达到了峰顶值——要8美元一蒲式耳。即使价格又回落到3.5美元一蒲式耳了，可依然还是高于历史标准。有些食品生产商在春夏两季囤积玉米和其他商品，因为他们担心价格会越来越高。但相反，价格下跌了，而他们现在还得付高昂的价格直至合约期满。

对牲畜产出商家而言，当成本上升时，他们常常不能立即提价，因为那些价格建立在公开的由供需关系支配的市场之上。他们取而代之的，是开始减小牛羊喂养的规模，那最终会导致市场肉类减少、价格上升。但减少牲畜产出也只能维持几个月到几年，临时起到实际抑制价格的作用，如果屠杀喂养的动物以减少产出的话。

更大食品通胀很可能激起一场有关其原因的大辩论。许多食品制造商和经济学家坚持，一个原因就是政府政策提倡大量使用由谷物提炼而来的乙醇燃料。

大约三分之一的农作物被用于制作乙醇，使得乙醇生产商同牲畜农场主以及食品制造商去竞争。他们竞争的结果，就是现在谷物的价格越来越高、越来越反复无常了。

“油价和农业商品的关系不同以往，就象2007年，它是那些食品生产企业的主游戏操控者。”咨询公司FarmEcon总裁FarmEcon说。

但乙醇拥护者反击，食品工业的争论是错误的，他们说，当乙醇生产加大时谷物价格却在跌落。Matt Hartwig，可再生燃料协会乙醇工业群体的发言人说，食品公司“很快会告诉美国民众，他们不得不加价是因为谷物是如此昂贵，谷物如此昂贵的原因就在于基于谷物而生产的乙醇。”

Hartwig先生补充道：“现在，我们非常清楚地知道，那种关系并不存在。如果乙醇不成其原因，那食品价格上涨真正的原因是什么？”