股债齐涨，投资者该怎么看？

股票和债券市场正在同时上涨——目前来说是这样。

市场在2019年上半年大幅上涨，但不能保证这种涨势会在今年的剩余时间里持续下去。不过有一点可以肯定，那就是股债双涨不是什么非同寻常的事。

截至6月底，标普500指数在2019年上涨了18.5%。彭博巴克莱美国综合债券指数同期上涨6.1%，该指数代表了美国债券市场的整体走势。今年上半年，60%美国股票加40%债券这样的简单投资组合的回报率为13.6%，创下自1997年上半年以来该组合的最好表现。

实际上，在1976年彭博巴克莱美国综合债券指数诞生以来， 60%/40%股债组合在上半年出现两位数涨幅的次数并不多，算上这次也只有11次。

有些投资者可能觉得股票和债券同时出现这样的大行情很奇怪。但在1976年到现在的43年里，股债双涨的年份共有32个。如果用5年期美国国债数据，我们还可进一步向前回溯。在二战以来的74年里，美国股票和债券同时上涨的有50年，约占三分之二。

有些人觉得股票和债券应该走势相反，所以上述情况是讲不通的。但多样化投资的全部意义就在于将不同市场环境下表现不同的资产组合到一起。问题是投资者经常弄不清楚如何看待投资组合中各种资产的相关性。大多数投资者都觉得应该持有负相关投资，也就是走势相反的资产。但人们真正应该持有的是预期回报为正的组合，而且其中各类资产的相关性会根据市场环境而逐步变化。

如果两项资产的相关性为1.0，就意味着其中一项资产的价格上涨时，另一项资产也会上涨；如果相关性为-1.0，则意味着一项资产上涨时，另一项资产就会下跌。相关性接近零则表示这两种资产的价格变动之间几乎没有关系。而从长期来看，股票和债券之间的相关性正是如此。1945年以来，标普500指数与5年期国债的相关性为-0.1，也就是说两者之间的表现几乎没有关联。但这种关系会随着时间的推移而改变，从下图中的3年滚动相关性数据就可以看到这一点。

Stocks and bonds are moving higher together -- for now.

The huge market gains in the first part of 2019 aren’t guaranteed to stick for the remainder of the year. But one thing is certain: It's not out of the ordinary for stocks and bonds to rise in concert with one another.

Through the end of June, the S&P 500 was up 18.5% in 2019. The Bloomberg Barclays U.S. Aggregate Bond Index, a proxy for the broad U.S. bond market, was up 6.1% at the halfway point of the year. A simple 60/40 mix of U.S. stocks and bonds returned 13.6% through the first six months of the year, the best start for this portfolio since the first half of 1997.

In fact, going back to the inception of the Aggregate Bond Index in 1976, this was just the eleventh time a 60/40 portfolio of stocks and bonds began the first half of the year up double digits.

It may seem odd to some investors that both stocks and bonds could be up so much at the same time. Yet, since 1976, stocks and bonds have both gained in the same calendar year in 32 out of 43 years. We can take things back even further using data on 5-year treasury bonds. Since World War II, U.S. stocks and bonds have seen positive returns in 50 out of 74 years or roughly two-thirds of the time.

This relationship might not make sense to those who assume stocks and bonds should move in different directions but the whole point of diversification is to combine assets that act differently during various market environments. The problem is investors often confuse how to think about correlations within a portfolio. Most investors assume you want to own negatively correlated investments that move in opposite directions. But what you really want is assets that have a positive expected return profile with correlations that change over time depending on the market environment.

A correlation of 1.0 implies that when one asset rises so does the other asset while a correlation of -1.0 implies when one asset rises the other one falls. A correlation close to zero implies little relationship in price movements, which is exactly what things look like for stocks and bonds over the long haul. Since 1945, the S&P 500 and 5-year treasuries have a correlation of -0.1, meaning there is little relationship in how they perform. But this relationship changes over time as you can see from the rolling 3-year correlation numbers:

跟金融市场上几乎所有其他东西一样，股票和债券之间的关系一直在变，但这实际上是件好事。债券在投资组合中大放异彩的时刻不是股价上涨，而是股价下跌，只有在这种情况下，人们才会希望负相关性发挥作用。

在1945年以来的74年里，标普500指数有16年下跌，平均跌幅为11.7%。而在这些年份中，5年期美国国债有15年都是上涨的，平均涨幅为6.2%。上一次股债同时下跌出现在1969年，当时标普500指数下跌了8%以上，5年期国债跌幅则不到1%。

The relationship between stocks and bonds is anything but static, like nearly everything else in the financial markets but this is actually a good thing. The true time for bonds to shine in a portfolio is not when stocks are up but when they’re down, which is the only time you want that negative correlation to kick in.

Since 1945, the S&P 500 has been down in 16 out of 74 years, with an average loss of -11.7%. In those down years, 5-year treasuries were positive 15 out of 16 times, with an average gain of 6.2%. The last time stocks and bonds were down in the same year was 1969, when the S&P fell more than 8% while 5-year treasuries were down less than 1%.

在这种时候，债券就可以证明自己在投资组合中的价值了。市场震荡时，债券能够为投资者提供稳定性，让他们有能力在股票下跌时补仓，或者把债市收益用于支出。

对于美国股票和债券投资者来说，2019年上半年差不多是最理想的阶段，但这种情况不会永远持续下去。好消息是，当股市不可避免地回落时，债券往往能够为他们遮风挡雨。（财富中文网）

译者：艾伦

审校：夏林

This is when bonds prove their worth in a portfolio, offering investors stability during times of volatility and the ability to rebalance into falling stocks or use bond proceeds for spending needs.

The first half of 2019 was about as good as it gets for investors in U.S. stocks and bonds. That won’t last forever. The good news is when the inevitable setback occurs in stocks, bonds tend to provide some shelter from the storm.