You are right, it was the SEC rather than FTC, my bad. But no, it was the late 1970s, not the 1990s.

There was clearly an SEC change for transparency of executive compensation that was driven by concerns of rising inequality in the early 1990s; I can't find anything about one in the late 1970s with that as a motivation, and it seems improbable, because through the 1970s the slow compression of wages following the 1940s “Great Compression” was still continuing, and significant rising inequality took into the 1980s to take off, and wasn't generally a concern of policymakers or in the political sphere in any significant way until the 1990-1991 recession.