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P/E Ratio -- Price-to-Earnings

P/E = Share Price / Earnings Per Share. It tells you how much investors are willing to pay for each dollar of profit. A high P/E means investors expect strong future growth; a low P/E means growth is expected to be slow.


Interpreting P/E

S&P 500 avg P/E: ~20-25x (fair value range).
  < 15x: potentially undervalued or slow-growth industry.
  15-25x: roughly market average -- reasonable for most companies.
  > 40x: high growth expected; valuation depends on future earnings.
  Negative P/E: company is unprofitable (common in early-stage tech/biotech).

P/E limitations

Backward-looking: uses trailing 12-month earnings.
  Forward P/E uses estimated next-year earnings -- more useful for growth stocks.
  Two companies can have the same P/E but very different growth rates.
  Always compare P/E to industry peers, not the whole market.

PEG ratio -- the better metric

PEG = P/E / Expected Earnings Growth Rate.
  PEG < 1: potentially undervalued relative to growth.
  PEG = 1: fairly valued.
  PEG > 2: expensive relative to growth expectations.
NVDA had a P/E of 60 but a PEG of 1.2 during peak AI growth -- actually 'cheap'.

✓ Quick Tips
  • High P/E stocks (50x+) are priced for perfection -- any miss causes violent drops.
  • Low P/E value stocks can stay cheap for years if growth doesn't materialize.
  • Use P/E to compare companies within the same sector, not across sectors.
  • Tech companies have naturally higher P/E than banks or utilities -- that's normal.

Related: EPS -- Earnings Per Share & Earnings ReportsMarket CapitalizationBull Market vs Bear Market

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