Kevin Plank is not lying. The CEO of Under Armour wants to invest $4.4 billion in Port Covington, but says he needs $1.2 billion in city, state and federal subsidies ("public investments") for this to make sense. This is God's truth.

The problem is the potent investment repellent that is Baltimore's property tax rate. According to Mr. Plank's plan, Port Covington will eventually have an assessed value of $2.6 billion, putting him on the hook for $59 million in annual property taxes.

If, instead, he built a similar project in Baltimore County, his tax bill would fall by $30 million. Every year. Forever.

This tax gap has fueled suburban sprawl and urban decay for decades — and has disparate impact on Baltimore's majority-minority population. Just in Freddie Gray's tragically short life, the city lost 111,000 jobs and 164,000 residents.

Blame "structural racism" for this if you want, but here's an inconvenient truth: Even if we waved a magic wand and eliminated all racism tomorrow — as wonderful as that would be — it still wouldn't make financial sense to develop real property in Sandtown-Winchester or, indeed, most of Baltimore.

This is why every major redevelopment project since Charles Center in the '60s has been subsidized, whether via TIFs (tax-increment financing for infrastructure that, out in the counties, is customarily paid for by developers), PILOTs (payments in lieu of taxes) or other tax credit programs.

All Mr. Plank has done is ask for the biggest subsidy yet. But he has done his math correctly.

Consider: If we gave him a $1.2 billion check (instead of "free" infrastructure), and he invested it at 2.5 percent, he'd earn interest of $30 million a year — exactly enough to offset the aforementioned tax hit in the city. So the requested subsidies enable Port Covington's economics to make sense, at least for Mr. Plank, despite the city's punishing tax rate.

But does it make sense for the city?

Critics on the left argue that Port Covington will be an enclave for the well-to-do, with little spillover benefit for poor areas in dire need of renewal. They're speaking God's truth, as well.

Part of this is geography. Mr. Plank's baby is the most isolated developable tract in the city. It might well be called Fortress Covington, cut off as it is from existing neighborhoods by water on one side, and railroad tracks and an elevated highway on the other.

Developers often plead for subsidies by invoking a "domino effect," promising that prosperity here will spread there. In this case, it's hard to imagine Covington's economic dominoes toppling to the other side of the tracks in South Baltimore, much less to the city's destitute east and west sides.

But the bigger problem here is not geography but economics. Lifting the city's self-imposed barrier to investment on Port Covington's 266 acres does nothing to remove it elsewhere. The same financial math that led Mr. Plank to demand his TIF will continue to apply in the rest of the city's 52,000 acres; this subsidy will no more reverse the city's decades-long economic decline than did previous ones for Harbor East or Harbor Point. This is weak medicine at best, and terribly inequitable because it is being withheld from those most in need.

For too long, city leaders have dismissed broad-based tax relief as unaffordable. But their eager embrace of Mr. Plank's audacious request itself challenges this claim.

Cutting the city's property tax rate in half would, indeed, cut receipts by about $400 million this year. The contemplated $1.2 billion in city, state and federal subsidies for Mr. Plank's project alone would cover three years of such losses.

But, of course, with a competitive tax rate the city would not only be attractive to Mr. Plank but to untold numbers of others who would like to invest in Baltimore but lack political muscle to win the concessions that would make this worthwhile. The city's tax base — its property values, its piggy-back income taxes from new residents and much else — would grow in exactly the way described by Port Covington's advocates. Just much more, faster and beyond "rich enclaves."

When San Francisco's confiscatory property tax rate was slashed by two-thirds via California's Prop 13 referendum in the late '70s, it had to tighten its fiscal belt for just three years before revenue growth from an expanding tax base more than offset the initial losses from the voter-imposed tax cap; it soon became a superstar city.

Scoffers say that "we're no San Francisco." But when Prop 13 kicked in, that city was losing population and jobs faster than Baltimore. What's preventing a similar renaissance here is our refusal to do for everyone what we're willing to do for Kevin Plank.

Stephen J.K. Walters is the author of "Boom Towns: Restoring the Urban American Dream" and a professor of economics at Loyola University Maryland. His email is swalters@loyola.edu.