At the risk of making too much hay over a couple of numbers, I give you 4.5 and 0.1 little noticed when they came out the other week but remarkably telling digits in examining the local economy.

For the month of September, Los Angeles County had an unemployment rate of 4.5 percent, an astonishing drop from 6.3 percent a year earlier and certainly the lowest it’s been in many, many years. Lower, in fact, than high-growth areas such as San Bernardino (4.8 percent) and Riverside (5.3 percent). Lower than the national rate of 4.8 percent.

This clearly shouldn’t be. Los Angeles County is a massive patchwork of urban ups and downs a mostly mature, very complex piece of business that mixes success stories on the Westside with chronic joblessness to the south and east. It’s too big and messy, in other words, to see such a precipitous drop over a mere 12 months.

Which is why the real rate is probably not quite that low. The state survey that measures unemployment each month is not always reliable because it’s hard to get a representative sample of county households. But the number can’t be all that wrong, and even assuming that it’s 4.8 percent or 5 percent, we’re still talking about a pretty thriving economy.

Actually, that’s been obvious for some time.

Look at the massive amounts of construction taking place, with permits issued through July up 7.3 percent from a year earlier. Look at the amount of television production throughout the city, with 100 of the 134 scripted and reality series being shot here and an estimated 132,000 workers fueling the boom. Look at the ports, where traffic has almost doubled in the past five years. Together, the Port of Los Angeles and Port of Long Beach account for one-third of the nation’s cargo shipments.

Beyond those very specific indicators, just look at your own community contractors turning down business because they have too many jobs (a throwback to the post-Northridge earthquake activity in the mid-1990s), the tree-pruning guy putting you off until next year, the house down the block being flipped for $100,000 more than what it sold for a year ago, the large number of “Help Wanted” signs popping up in store windows.

For those convinced that California is inhospitable to business, it must be a tad disorienting. Or don’t you remember then-candidate Arnold Schwarzenegger claiming in the summer of 2003 that “there are more businesses leaving California now than ever before.”

There’s just one problem it’s not true, not then and not now. Which brings up that second number.

In studying companies leaving California between 1993 and 2002, the Public Policy Institute of California concluded that the number of net jobs lost in any one year was never greater than 0.1 percent. It turns out that the loss of jobs had less to do with businesses leaving the state than businesses just failing. Even California’s tech sector did noticeably better after the dot-com collapse than other states in terms of job loss.

(Time out for the editor to gloat: The Business Journal, in its Sept. 1, 2003 edition, noted that more California-based businesses were buying out-of-state businesses than the other way around. We based our conclusion, not on vague anecdotes spewed out by the Schwarzenegger crowd, but on a quantitative data dump of inflows and outflows.)

And what about those who insist that the state’s business growth has been stifled by high taxes and excessive regulations? Those are certainly irritants to any bottom line, but in most cases they don’t ultimately determine a company’s success. If they did, California wouldn’t have any companies left.

Yet we do, lots of them, and many of them are making very good money. It’s weird but true that beyond all the obvious bad stuff schools, traffic, outsourcing, inflation, housing affordability the economy continues to rock. We’ll see how long it lasts.

Mark Lacter is editor of the Business Journal. He can be heard every Tuesday morning at 6:55 and 9:55 on KPCC-FM (89.3).