Slow But Steady Progress

What's the word that means slow but unstoppable?  I'll know it when I hear it.  Anyway, that word seems to apply here:

A new survey of 461 colleges and universities around the country found that roughly one in three schools still maintain policies that drastically limit free speech on campus.

According to an annual study conducted by the Foundation for Individual Rights in Education (FIRE), 32.3 percent of colleges and universities surveyed “received FIRE’s lowest, red light rating for maintaining speech codes that clearly and substantially restrict freedom of speech.”

The “Spotlight on Speech Codes” report, however, notes that the percentage of red light institutions has been consistently shrinking throughout the last decade, pointing out that “This year’s figure is seven percentage points lower than last year and almost 42 percentage points lower than in FIRE’s 2009 report.”