This article in Reuters not only applies to America but also to the United Kingdom, Germany, Switzerland etc.. It is simply the case that tax fraud is a Gentlemen`s crime and there is not need to investigate many Prosecution Offices conclude. This is mostly due to lack of understanding of the offshore structures, willful blindness and more importantly competency and systemic corruption.
An example is the Greek 40-40-20 rule. The penality issued by Greek`s Tax Authorities is know to have the following methodology: 40 % for the tax evador, 40 % for the tax investigator and 20 % for the Government.