Descripción: “...The first theory treats the underground economy problems, structures and changes in the laboral marketing. It shows than inmigrants in different cities do not find employment in modern economy; in this case, inmigrants look for subemployment.The next theory relates the underground economy and its incomes, shows that uneven incomes and high costs are translated  in obstacles to generate formal enterprises in the same way, regarding good and services demand and consumer low budgets prompt  background economy marketing.Another theory, claims the background economy as a result of the official system relates to the regulations and absence at regulations. ...”

Descripción: “...Ambas señales se emiten por dos canales separados y conforme se hace la prueba se van detectando los umbrales de mínima presión sonora audible. ...”