As Mayor Bill de Blasio maneuvers into campaign season, it’s the economy, stupid.

In his State of the City address on Monday, the “affordability crisis” got top billing. He plans to address it by creating new jobs and building more affordable housing.

Affordable housing has been a big focus for de Blasio, and how voters perceive the success of his efforts looks to be central to his re-election bid.

Early in his term, he touted his “Housing New York” promise to build or preserve 200,000 units of affordable housing in the next 10 years, and much of his political capital has gone into hitting that goal. In January, he celebrated the progress so far, announcing that over 62,000 affordable units had been financed since 2014.

But that figure hides the whole story. And part of the equation isn’t even being tracked by the city.

Not all affordable housing is new affordable housing

De Blasio is careful to say that the affordable units gained so far include those “built and preserved.” That technicality is important, because for the units de Blasio celebrated, twice as many are being “preserved” as built.

“Preserved” means the units were already affordable under a federal, state or city program. Those programs, typically subsidies to the landlord, can come to an end. Someone has to step in to preserve the status quo.

The city did that for some 41,600 homes out of the 62,000. For example, at a building in Williamsburg, the city convinced the owner to accept a preservation agreement (and funding) to keep the rent affordable for another 35 years. Under that agreement, none of its units go for more than $1,000 in a neighborhood where average rent is $1,000 per month, according to the city.

That’s a good deal, but it’s the same deal those residents had in the first place. It stems the tide of rising rents, rather than turning back the flow.

If the city can’t close the deal on a preservation agreement we lose drastically-needed affordable housing. Naturally, that can happen. Yet the city does not systematically track how many apartments are lost from the affordable pool per year in this way.

How do you make progress if you don’t know where you started?

There is an alphabet soup of subsidies offered by the city, state and federal governments, sometimes with the layers overlapping.

There are, for example, Low-Income Housing Tax Credits (LIHTC), administered by both city and state. In one version of preservation agreements, the city has to negotiate to re-up after 15 years.

Or Mitchell-Lama housing, one of the more well-known and productive creators of affordable housing. Some developments are now run by the city, while others are state-controlled.

When terms end and an agreement can’t be reached, a lot of units can go on the open market. That happened in a big way about ten years ago, says Thomas Waters, a housing specialist at the Community Service Society of New York. Mitchell-Llama properties were being bought and taken out of affordability programs. “A huge share of the stock was lost in that way.”

That ended to some extent with the 2008 financial crisis and we’re in a more stable period now with fewer units being lost: some 1,400 Mitchell-Lama units over the past four years, whereas over 5,000 were lost in 2006, according to Waters.

Waters can say that confidently because he compiled what might be the most comprehensive data on “lost” affordable apartments, culled from 12 years of city, state and federal sources. But his database lacks many buildings with subsidies operated by the city’s department of Housing Preservation and Development.

Shouldn’t the city have a better idea of the status of its affordable programs, given the big focus from de Blasio?

HPD says property owners are required to notify the agency and ask for “permission” when their subsidy agreements end, which seems to indicate that it would be difficult for those to fall through the cracks. But the lack of official numbers means it’s hard to evaluate the actual net benefit New Yorkers are getting from de Blasio’s housing push.

And the push must continue, pre- and post-mayoral campaign. Waters says that some properties receiving LIHTC benefits are coming to the end of their term in 2020.

Many stand to be refinanced and stay affordable, but for apartments in high-rent areas, the price will have to be right to convince owners to stay with the program. Another year, another affordable housing fight.