Strikes — organized labor’s ultimate bargaining chip — have become a workplace relic.

In the 30 years that have passed since Los Angeles teachers last walked off the job, work stoppages nationwide have fallen by two-thirds as union clout has nearly halved. I filled my trusty spreadsheet with U.S. jobs and pay data to show how major strikes — defined as involving 1,000 or more workers — have become a rarity, even if there’s been a mild uptick of late. Meanwhile, union memberships have tumbled in the private sector.

In 1989, there were 51 strikes nationwide at a time when union members represented 16.4 percent of all workers. Note the industry split: union rolls equaled 12.3 percent of private-sector employees and 36.7 percent of government jobs. Fast-forward to 2017: Only seven strikes nationwide as unionized workers equaled 10.7 percent of all workers — but that’s merely 6.5 percent of private-sector employees (roughly cut in half in 30 years) and 34.4 percent of government jobs (only a small drop).

By the way, last year’s preliminary data shows 17 strikes were the highest in six years. Union membership data is not yet available.

A little history lesson is in order. Union muscle nationwide ebbed dramatically after President Ronald Reagan broke the air traffic controllers’ union in 1981 by firing government workers who walked off the job.

Strike counts show a steep reduction in the years since.

From 1947 to 1981, there were an average 296 strikes annually nationwide. From 1982 through 1999, the pace fell to 47 a year. And in this modern century? Just 17 a year.

Let’s note that American income growth has cooled in a pattern similar to unions’ overall clout.

From 1948 to 1981, real disposable U.S. income — that’s after taxes and inflation — averaged 3.9 percent annual gains. Since then, a U.S. family’s purchasing power has risen at only a 2.9 percent yearly pace.

And let’s also remember what’s soared since 1981 — the stock market!

The S&P 500 stock index rose as an average 4.9 percent pace between 1947 and 1981. Since Reagan’s blow to unions — and the ensuing decline in pay raises — stocks have soared at a 9.7 percent annual rate.

Just like many parents of school-age kids, Wall Street hates strikes, too!