除卻技術分析或直覺炒股法外，不論是投資證券、存錢進銀行、買樓收租，甚至自己開公司做老闆，也涉及估值的問題。
單以股票來說，可把估值法分類為相對估值和絶對估值。相對估值即是大家熟悉的市盈率﹝P/E﹞、市賬率﹝P/B﹞等，由於使用時需要跟相同行業的股票一拼比較，因此歸類為相對估值。另外，較為常用的絶對估值方法則有現金流折現法(Discounted Cash Flow, DCF)，今篇文章會先捨易取難，討論DCF。
現金流折現法主要由兩個概念組成：1) 資金的時間值，和2) 股東能從公司獲得的回報。先從第一點說起，如果我有$100以3%年利率存放在銀行，一年後便可無風險的收取$3利息，換句話說一年後的$103，便相等於現在的$100，這$3的相差便是資金一年的時間值。再推演一步，如果在銀行的無風險利息以外，還有另一項有虧損機會的投資可供選擇，經分析後，為了補償這項風險投資或造成的損失，我會要求在銀行的3%存款利率以上，再加6%的補償，即要有9%的回報才足夠吸引我冒這個風險，我們稱這要求回報率為股本成本，亦即下文公式將用到的折現率(Discount Rate, 將未來預期的收益折算成現值的比率)。接著第二點，股東能從公司獲得的回報又是甚麼呢？大多數人想到的第一個答案是公司派發的股息，其他的回報種類還有巴菲特使用的”Owner Earnings”概念。
以股息為公司估值十分簡單，只要公司周期性比較低，而且將來的派息可測性高，都可以使用股息折現模型(Dividend Discount Model, DDM)計算公司的合理值。其公式是每股股息﹝D﹞除以折現率﹝r﹞和長期股息增長率﹝g﹞之差：D /﹝ r - g﹞ --- 公式(1)。以下以昨天討論過的TVB (0511.HK)作例子：
TVB是一家成熟而派息穩定的公司，我們通過對公司業務的分析，預期今年將派發$2.02股息，未來股息亦能跟隨通漲以約3%增長直至無限年以後﹝即2010年股息為$2.02，2011年$2.08，2012年$2.14…﹞，而回報要求(折現率)則設定為8%。把以上資料套入公式(1)，得出合理值為：$2.02 / (8% - 3%) = $40.4。當然，這只是理論值，股價並不可能跟著這個主觀的估值走，因此實戰中的買賣策略應根據市場情況作出調整，並最好進一步以樂觀和悲觀的假設計算出一個估值範圍，這個範圍有點類似統計學上的置信區間(Confidence Interval)，使交易時對股價變化有一個「譜」。
除了TVB，我們也曾使用相同方法為隆成集團(1255.HK)估值，如有興趣可參考：http://hk.myblog.yahoo.com/sober-man/article?mid=386。下篇將討論一些使用DDM時要注意的細節。
所有估值方法都有局限性，對於從不派息的公司，DDM便不可用了。對於其他困難，除了使用其他適合的估值方法外，就以DDM而言，也可以把模型修改或加強，例如可以把以上討論的一個階段DDM，變成多階段DDM。 選擇折現率是藝術，可使用教科書的方法，也可憑經驗直覺。 請緊記著，不要過份迷信模型，使用估值模型的大方向是避免準確的錯誤，對背後的實體公司的理解才更重要。
以下是巴菲特對選擇折現率的看法： "We don't discount the
future cash flows at 9% or 10%; we use the U.S. treasury
rate. We try to deal with things about which we are quite certain. You
can't compensate for risk by
using a high discount rate."
"In order to calculate intrinsic value,
you take those cash flows that you expect to be generated and you discount
them back to their present
value - in our case, at the long-term Treasury rate . And
that discount rate doesn't pay you as high a rate as it needs to. But you
can use the resulting
present value figure that you get by discounting your cash
flows back at the long-term Treasury rate as a common yardstick just to
have a standard of
measurement across all businesses."
"In
a world of 7% long-term bond rates, we'd certainly want to think we were
discounting the after-tax stream of cash at a rate of at
least 10%. But that
will depend on the certainty that we feel about the business .
The more certain we feel about the business, the closer we're willing to
play. We have to feel
pretty certain about anything before we're even interested
at all. But there are still degrees of certainty. If we thought we were
getting a stream of cash
over the thirty years that we felt extremely certain about,
we'd use a discount rate that would be somewhat less than if it were one
where we expected
surprises or where we thought there were a greater possibility
of surprises."
以下是巴菲特對選擇折現率的看法： "We don't discount the
future cash flows at 9% or 10%; we use the U.S. treasury
rate. We try to deal with things about which we are quite certain. You
can't compensate for risk by
using a high discount rate."
"In order to calculate intrinsic value,
you take those cash flows that you expect to be generated and you discount
them back to their present
value - in our case, at the long-term Treasury rate . And
that discount rate doesn't pay you as high a rate as it needs to. But you
can use the resulting
present value figure that you get by discounting your cash
flows back at the long-term Treasury rate as a common yardstick just to
have a standard of
measurement across all businesses."
"In
a world of 7% long-term bond rates, we'd certainly want to think we were
discounting the after-tax stream of cash at a rate of at
least 10%. But that
will depend on the certainty that we feel about the business .
The more certain we feel about the business, the closer we're willing to
play. We have to feel
pretty certain about anything before we're even interested
at all. But there are still degrees of certainty. If we thought we were
getting a stream of cash
over the thirty years that we felt extremely certain about,
we'd use a discount rate that would be somewhat less than if it were one
where we expected
surprises or where we thought there were a greater possibility
of surprises."
沒有留言:
發佈留言