theory Pecking order theory tries to capture the costs of asymmetric information. It states that companies prioritize their sources of financing (from internal financing to equity) according to the law of least effort, or of least resistance, preferring to raise equity as a financing means "of last resort". Hence, internal financing is used first; when that is depleted, debt is issued; and when it is no longer sensible to issue any more debt, equity is issued. This theory maintains that businesses adhere to a hierarchy of financing sources and prefer internal financing when available, and debt is preferred over equity if external financing is required (equity would mean issuing shares which meant 'bringing external ownership' into the company). Thus, the form of debt a firm chooses can act as a signal of its need for external finance. The pecking order theory has been popularized by Myers (1984) when he argued that equity is a less preferred means to raise capital, because when managers (who are assumed to know better about true condition of the firm than investors) issue new equity, investors believe that managers think the firm is overvalued, and managers are taking advantage of the assumed over-valuation. As a result, investors may place a lower value to the new equity issuance. Capital structure substitution theory The capital structure substitution theory is based on the hypothesis that company management may manipulate capital structure such that earnings per share (EPS) are maximized. The model is not normative i.e. and does not state that management should maximize EPS, it simply hypothesizes they do. The 1982 SEC rule 10b-18 allowed public companies open-market repurchases of their own stock and made it easier to manipulate capital structure. This hypothesis leads to a larger number of testable predictions. First, it has been deducted that market average earnings yield will be in equilibrium with the market average interest rate on corporate bonds after corporate taxes, which is a reformulation of the 'Fed model'. The second prediction has been that companies with a high valuation ratio, or low earnings yield, will have little or no debt, whereas companies with low valuation ratios will be more leveraged. When companies have a dynamic debt-equity target, this explains why some companies use dividends and others do not. A fourth prediction has been that there is a negative relationship in the market between companies' relative price volatilities and their leverage. This