Thesis: This thesis starts, theoretically, with the informativeness of signals when information is imperfect, followed by the applications on the credit and tabor markets. In chapter 2 we show that Blackwell's informativeness criterion can imply the dispersion of the conditional expectations – the supermodular dispersion criterion proposed by Ganuza and Penalva (2010), only when the signal is binary. Links between the dispersion of the conditional expectations and Persico's accuracy criterion can be built up but with strong restrictions. In chapter 3, we consider a lender-borrower relationship where borrowers can choose to disclose their private information by paying a non-negligible cost. The decision of information revelation is endogenized, and so is the market opacity. We show that there exists only opaque (transparent) equilibrium when the safe interest rate is low (high) enough; there are multiple equilibrium when interest rate is intermediate and credit crunch may happen. The model is then extended to an OLG context and we show that the market may converge either to an opaque or a transparent stationary state, or, for some configurations of parameters, have permanent oscillations between different states. In chapter 4 we study the impact of hiring discrimination on workers' skill investment decision in a directed search model. Both the discriminated and favored group can underinvest in skills in equilibrium. Whenever one group underinvest, the other remain high skilled and firms suffer from lower profit compared to the economy where discrimination is absent.