<p>In this article a jurisprudential and legal analysis of the updated base income for liquidation of the first monthly pension, coming from pensions established before being in force the Constitution of 1991, the 100th law of 1993 and pension regimes which are parallel for having had conventional origins. It is methodologically developed into three chapters: i) An introduction to the subject under study in which the following conceptual references are explained; the right to social security, old-age pension and indexing; ii) A study on indexing and constitutional jurisprudence effects on constitutional regulatory principles protecting the rights of the elderly, such as fairness, dignity and the theory of acquired rights, among other precepts of constitutional status ; iii) conclusions, which are not intended to be the final word, but rather to generate new insights about it.</p>