There are many other yields to compare them to, but for purposes of isolating factors having to do with growth, the most useful is to compare equity yields with bond yields, especially government bonds.

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And as he points out, there may be other reasons to believe that big investors' love affair with bonds, especially government bonds, may be supplanted by a restored affection for equities - or to use the dreadful jargon, this may be a year of "rotation" out of debt and into shares.

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Buying municipal bonds is more complex than buying stocks, especially since government entities can have bonds with varying maturities and yields.

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