I think the question is, when does a rally in the market go from:
1) prices moving up based on fundamentals, and new information that leads to increased valuation
to
2) prices increasing due to the "greater fool theory"
The beginning of any rally could be justified or appropriate given the addition of new information to investors. But what if the Dow went up 100 points every day from now until the end of May? At some point, a rally becomes attributable to mass frenzy and a correction is inevitable. The magnitute should be proportional to the size and speed of the run-up.
1) prices moving up based on fundamentals, and new information that leads to increased valuation
to
2) prices increasing due to the "greater fool theory"
The beginning of any rally could be justified or appropriate given the addition of new information to investors. But what if the Dow went up 100 points every day from now until the end of May? At some point, a rally becomes attributable to mass frenzy and a correction is inevitable. The magnitute should be proportional to the size and speed of the run-up.