In 2009, just 22 homes in Portland sold for more than $500,000. What a difference five years makes: For the past 12 months, that number is 75. South Portland’s rise is nearly as steep: from 4 to 12 homes in the “luxury” category.

This jump in top-shelf housing pric

Portland sales over $500,000, in 2009, and 2014. MREIS data

es is probably not a matter of existing houses selling for more. They are selling for more, but not that much more. What’s at work here is a new demand for new housing on the Peninsula. The demand for new construction, with parking, energy efficiency, water views, fine finishes, and perhaps a private elevator, is what’s new. And that stuff costs money.

South Portland home sales over $500,000, in 2009 and 2014. MREIS data

In a more gradual process, existing housing is also spiffing up and pricing up.

South Portland, by which I mean the east side of South Portland, is showing a more organic growth pattern. There, it’s renovation that’s raising the prices. As time-worn bungalows and colonials hit the market, they’re updated, upgraded, and spit-polished to meet the standards of a new demographic.

So what does it meeeeeeeean, this sudden jump in swell digs?

I think it could mean a more balanced demographic, particularly for Portland. The City hosts more than its share of expensive social services and tax-exempt organizations. That dumps more of the tax burden onto residential and commercial buildings. The high-end building boom will spread the property tax burden more widely.

Does it make Portland — and South Portland– less affordable, more homogenous, and less, you know, fabulously weird? Gradually, probably: Yes. And that’s what cities do: They swell and shrink, breath and cough, reflecting the mass movements of individual human beings.