When did the phrase "above your paygrade" come into use?

I heard this phrase in the current movie "The Post" and suspect it is an anachronism. Was this phrase in use in 1971?

My first instinct would be that this is quite an old expression, although it was likely used in a military or otherwise ranked and graded environment. It may be a bit more recent than I thought though. I found this link on quoteland.com where user thenostromo cites a source that is, alas, no longer available. It is however, archived by the WayBack Machine - thank you @DanBron for the link!:

The oldest use of "above my paygrade" only dates to 1999 on google news archives, from a chat transcript with gossip writer Lloyd Grove. However, searching for "above my pay grade" with a space yields older sources, going back to a 1981, which appear to have a military origin. In 1981, it came from a quote from Navy Secretary John Lehman in a UPI story.

Quote: “There has been no decision on Admiral Rickover’s extension (in the job) and it really is a decision that is above my pay grade" ~ Navy Secretary John Lehman

Its use by a military pilot in 1986 at least received notice by one columnist. It continues to be mentioned most often in military settings until the early 1990s, when it began to be more broadly used by US government officials. In July 1996, USAtoday described US republican congressperson Susan Molinari as someone who "uses hip phrases like above my pay grade and totally iced."

So that would indicate an early '80's origin of the expression, making your '71 quote indeed anachronistic.

However, another user, Bobby Stafford, on the same page quotes from personal experience:

I spent 20 years in the U. S. Army, beginning in 1966. I heard that phrase almost from the beginning, perhaps even once or twice in basic training. For those not familiar with the difference between 'rank' and 'grade': Rank is a titled designation, such as 'private' or 'sergeant.' Grade is actually for 'pay grade.' Enlisted soldiers grades range from E1 to E9, with equivalent ranks being private, corporal/specialist, etc., through Sergeant Major.

More than once I would ask a superior what a certain decision would be, and he would say, "That's above my pay grade." Meaning, of course, "I don't have the rank to make those decisions."

It's a military cliche I've heard for over 45 years.

So, if you trust this person, the expression has at least been in use since 1966, albeit in a military context. Whether your '71 quote is an anachronism would then largely depend on the context in which it was used.

Marlon M. Hanks, in 1955, takes the cake (so far) for performing beyond her pay grade:

...clerk-typist in the Supply & Fiscal Department, U.S. Naval Construction Battalion Center, Port Hueneme, is the winner of a $100 Superior Accomplishment award for performance of duties far beyond her pay grade and assignments.

Press-Courier, Oxnard, California, 30 Mar 1955 (paywall).

This should not come as a surprise; women routinely perform far beyond their pay grade.

For above the pay grade, a 1958 use is the earliest I've found so far in the particularized (to individuals or specfic groups of individuals) sense of "above one's level of professional responsibility" (OED):

At an advanced base no man can expect to be limited to the duties outlined for his billet. He may have to do some work that is above his pay grade, and he may, just as often, have to take on dull tasks and do them cheerfully.

Mineman 1 & C, prepared by Bureau of Naval Personnel, 1958.

Uses of the phrase "above ... pay grade" in a generalized sense are fairly common in the 1940s and 1950s in military contexts. For an example of such use in a generalized sense, this from 1940:

With the automatic pay raise, the applicant accepting enlistment is assured that at least after four months of service his pay will jump to $30 per month. His promotions above that pay grade are left almost entirely up to the man himself.

The Jackson Sun, Jackson, Tennessee, 29 Sep 1940 (paywall).

By the 1970s, the phrase in the particularized (to individuals or groups of specific individuals) sense is well-established in military contexts.