Congress, under pressure from their constituents, after continuously taking advantage of insider trading law exceptions to enrich its members, made insider trading by its members illegal in 2012 (this was known as the STOCK act, bill S.2038) The mechanism to enforce this was public access to the records of the members of congress.
Then, the 113th congress quietly passed bill S.716.ES into law (how quietly? Unanimously, no debate, no recorded vote, total voting time: 14 seconds), which eliminated public access to the relevant records of the president, vice president, any member of congress, and any candidate for congress.
Obviously, members of congress are in the perfect position to know about many advances and changes with regard to corporate value fluctuations. They make the laws that cause many of those value fluctuations, and then of course there are the lobbyists.
If I had access to this information for several years, as do congress members, I'm sure my net worth and that of my family members would be quite different from what it is now too.
But hey, no one cares. 'Murica, right? Let's get those tech jobs sent overseas and fluff the green carded cheap tech skilled workers while we stop the Terrible Threat Of Unskilled Immigrants. Perhaps then I'll be able to utilize my extensive programming skills doing... yard work. Thanks, congress. Thanks, corporations.
Congress: 14% approval rate, 94% re-election rate. You explain it. I can't.