It has been a reliable fact of life for investors, corporations and ordinary borrowers: interest rates, for the most part, keep heading lower.
But all of that may be about to change. For prospective homeowners, the cost of mortgages has been going up in recent weeks. Governments are also facing the prospect of higher borrowing costs down the road, and they are projecting increases to their debt burdens. Savers with money in bank accounts, on the other hand, have the prospect of finally earning more than a pittance on their deposits.
The interest rate charged by lenders, often cited as the single most important factor behind economic decisions, has been steadily going down for most of the time since the early 1980s, and has fallen to historical lows since the financial crisis. Over the last few months, though, investors and banks have been demanding higher payments for their loans, pushing up interest rates and bond yields.
The first tremors have been felt most sharply on investment products that were reliant on low rates, like bonds issued by American companies. But the movement is quickly spreading out into the real economy.
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"I think you all should be ready, because rates are going to go up," Jamie Dimon, the chief executive of JPMorgan Chase, told a financial industry conference at the Waldorf-Astoria Hotel in Manhattan on Tuesday.
As investors brace themselves for a new era of higher interest rates, global markets in bonds, currencies and stocks have experienced spasms of turmoil. On Tuesday, the catalyst for the market's volatility was disappointment over the Bank of Japan's decision not to take new steps to address rising bond yields. That heightened worries that other central banks — the Federal Reserve in particular — will soon pull back on pumping money into the financial system.
Since the financial crisis of 2008, the Fed has taken unprecedented steps to reduce rates, in an effort to stimulate borrowing and economic growth and bring down the unemployment rate. Recently, though, Ben S. Bernanke, the Fed chairman, signaled that the central bank could scale back its efforts in coming months if the economy improved. But there is much debate on Wall Street over what Mr. Bernanke is planning and when it might take shape.
Several prominent money managers say they believe that the economic recovery is weakening, which will make it impossible for Mr. Bernanke to pare the central bank's intervention and could lead to falling rates again. Interest rates have experienced temporary spikes a number of times in recent decades before heading back down.
But recent economic reports, including last Friday's job report, suggest that the economy is slowly recovering.
In anticipation of what the Fed may do, many on Wall Street have been preparing their portfolios for a future in which interest rates do not remain at the low levels of the last few years. In a survey of 500 large investors, 43 percent said they were planning to cut back on their exposure to bonds this year, while only 16 percent are planning to increase it, according to the asset manager Natixis.
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The recent efforts to adjust to higher bond yields have already been messy. Investors have been piling out of supposedly safe bond funds that have been a source of reliable returns in recent years, creating unexpected volatility in the markets.
Big American asset managers who borrowed money to buy foreign stocks and bonds have recently been selling those holdings, hurting markets around the world. That has been worsened by data suggesting that economic growth may be slowing outside the United States.
The realignment in the markets was evident on Tuesday as Asian and European stock markets fell. In the United States, stocks swung widely, with the benchmark Standard & Poor's 500-stock index closing down 1.02 percent. Treasury prices fell, pushing the yield on the benchmark 10-year Treasury note as high as 2.29 percent — its highest level since April 2012 — before settling at 2.19 percent. The Japanese yen strengthened 2.8 percent against the dollar.
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Many market specialists say they think that a transition could go more smoothly in the long run if interest rates continue to rise as the United States economy grows. Still, even in that optimistic situation, a wide array of market participants will have to shift their operating procedures and assumptions from a world where declining interest rates were a given.
"When past performance has been so consistent, the risk that investors underestimate the risk, I think has consistently been an issue," said Richard Ketchum, the president of the Financial Industry Regulatory Authority, which oversees brokers.
The recent market volatility highlights the connection between Wall Street investors and consumers. Banks set mortgage rates in line with the yields on mortgage-backed bonds, for example. So as a sell-off has hit the market for such bonds, causing their yields to rise, ordinary borrowers end up paying more.
The rising cost of a new mortgage has already pushed down the number of people refinancing old mortgages, putting a crimp on a recent source of extra income for many households.
The looming question now is whether higher mortgage rates could stall the rally in home prices that has been taking place across the country.
Many real estate analysts say that homes are so affordable that even a considerable rise in interest rates would not do much to undermine the housing recovery, especially if the economy is growing at a healthy rate.
"There's no strong correlation between interest rates and home prices," said Douglas Duncan, chief economist at Fannie Mae.
But Joshua Rosner, a managing director at the research company Graham Fisher & Company, said many Americans were still so heavily indebted that even a small rise in mortgage rates would hit the housing market. "Affordability is already a problem, and rising rates won't help that," he said.
For governments around the world, a rise in rates will eventually push up their borrowing costs at a time when they may still be grappling with fiscal deficits. Some countries will probably be able to take a steady increase in their stride. But a jarring wave of selling has recently hit certain bond markets in Latin America and Europe, pushing up borrowing costs for governments there.
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Recent market moves have also been an unpleasant jolt for ordinary savers who have come to view bonds as a stable anchor for any retirement account. The Vanguard total bond market mutual fund fell 2.7 percent last month after returning a steady 5.4 percent a year since 2008. Funds holding junk bonds, which were one of the hottest investments in recent years, have suffered even more.
Some managers argue that the important thing is to shift between different types of bonds, de-emphasizing longer-term, government-issued bonds. But whatever the mix, it is likely that bonds will present a risk to investors that they have not in recent history.
"There's no doubt we're living through the end of a generational bull market in bonds," said Scott Minerd, the chief investment officer at Guggenheim Partners.
—By Nathaniel Popper and Peter Eavis of The New York Times