California has an official state flower (poppy), an official state insect (the dogface Butterfly), even an official state theater (the Pasadena Playhouse). But no official state sport.

Unless you count the great Californian pastime of overestimating our population growth.

It probably should be enough that we’re the most populous state in the Union. But California’s own collective identity—for good and for bad—is so tied up with our size that we’ve become 38.7 million serial exaggerators.

We overestimate our present population; for the past decade it’s been routine for politicians and pundits to talk about our “state of 40 million,” even though we still haven’t reached 39 million. And you can’t trust on predictions of future population either. Californians have been talking for more than a generation about how we will have 50 million residents by 2020—and about us reaching 60 million or 75 million by the middle of this century (Gov. Schwarzenegger once suggested in my presence that we’d get to 100 million someday soon.) Gov. Jerry Brown invoked the 50 million figure last month in urging Californians “to find a more elegant way of relating to material things.”

The trouble is that, at our current pace, we’ll barely have 40 million people by 2020. While few Californians realize it, for the past 20 years, the state has seen a massive slowdown, with immigration flattening out and the birth rate falling below the level of replacement. The result: California is experiencing the slowest rates of population growth in our history and what the Public Policy Institute of California has called “an unprecedented migration of residents to other states.”

In the last few years, the state government has been rapidly ratcheting down its long-exaggerated predictions of future growth. Consider this: In 2007, the state department of finance projected that California would reach 50 million by 2032. By 2012, that milestone had been delayed until 2049. In the most recent revised projections based on 2014 figures, we don’t hit 50 million until 2051.

Why do we keep overstating our numbers? There are two big reasons—one nice, and one quite nasty—for the exaggerations.

The nicer one is our deep attachment to the 1980s, those salad days back when people came to our state in droves and L.A. hosted the Olympics. It was in 1985 that the Population Reference Bureau first made the 50-million-by-2020 prediction, and the U.S. Census Bureau was still echoing that in the mid-1990s. Such projections made sense then—given California’s 20th-century growth from less than 2 million people in 1900 to more than 33 million in 2000.

Until very recently, our demographers, perhaps too attached to their leg warmers and Van Halen records, have found it hard to shake those earlier growth assumptions. Even in the late ’90s, when it was clear that the early ’90s recession had changed California’s trajectory, the state still had us reaching 45.5 million by 2020, and the Census thought we’d make 49.3 million by 2025.

When I pressed USC demographer Dowell Myers about his profession’s knack for overestimation of California’s population, he offered this thesis: “Everyone—officials and citizens—is operating with outdated narratives of change in California that date from 1990 and earlier.” He added: “Only after the Great Recession and a second consecutive decade of extra-slow growth did it finally become clear to state demographers that growth was NOT going to return close to the level of the unprecedented 1980s.”

Disturbingly, that means we are making all kinds of decisions about state policy –including about school, housing, other infrastructure, and immigration—on false premises. Which brings me to the nasty reason for the persistence of these false assumptions about rapidly growing population—the assumptions serve the ideologies of both the left and the right.

On the left, those warning of the environmentalist apocalypse rely on the Malthusian notion that California is being doomed by endless growth, which in their view must be stopped. That’s allowed them to justify opposing the essential replacement of aging infrastructure, and the adoption of new energy sources. The twisted logic goes something like: “Don’t build it, and they won’t come.” The New York Times, in a series of recent front-page editorials masquerading as news stories, has taken up this line, arguing that California is growing unnaturally fast and is thus pushing up against Mother Nature’s limits.

On the nativist right, the narrative of endless population growth serves a different cause. The anti-immigrant set is even blaming the drought on an imagined population growth from a supposed surge in immigration that is not in fact taking place. While California has 10 million foreign immigrants, most of them have been here a lot longer than you (nearly half are citizens).

Our population overestimates are a close cousin of the assumption—made either triumphantly or apocalyptically, depending on who you are—that Latinos are somehow taking over California. USC’s Manuel Pastor has called this the “idea that California is on its way to becoming 150 percent Latino.” Indeed, with the slowdown of border crossings and a plunging birth rate among Latinos, our ethnic mix is no longer changing so fast. Demographers who once predicted Latinos would soon become a state majority now say it’s possible that Latinos will never represent a majority in California.

The irony, unappreciated by the environmental left and anti-immigrant right, is that they have already won. California’s population is not growing out of ecological or demographic control.

The trouble is that so few of us recognize this reality or have responded to it. The narrative that we’re being overrun by newcomers crashing our nirvana is understandably seductive. But California, with fewer children and a stagnant population, needs to do more for those children, since they will have to be more productive than previous generations. And if we want to have the economic growth to support an aging population and generous social benefits, we need to think—for the first time—about how to attract more people here from other states and other countries, and to do a better job of retaining the people we do have.

Unfortunately, there is little serious effort or investment aimed at growing our actual population. Perhaps because we’re too busy coping with the population boom taking place in our collective imagination.

Joe Mathews is California & innovation editor for Zócalo Public Square, for which he writes the Connecting California column.