Valuation
Shares are valued according to various principles in different markets, but a basic premise is that a share is worth the price at which a transaction would be likely to occur where the shares to be sold. The liquidity of markets is a major consideration as to whether a share is able to be sold at any given time. An actual sale transaction of shares between buyer and seller is usually considered to provide the best prima facie market indicator as to the "true value" of shares at that particular time.
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