Now that we have 2010 census data, we can take another look at the continuing story of the two — or, more accurately, three — Maines. And the picture isn’t pretty.

Over the two decades since 1990, Maine’s so-called rim counties — the six most rural counties bordering Canada, running from Oxford in the west, up to Aroostook in the north and over to Washington in the east — saw their total employment (meaning both wage and salary employment plus self-employed sole proprietor jobs) actually decline by nearly 1,000 jobs.

In the central counties — Androscoggin, Kennebec and Penobscot — total employment grew by more than 23,000 jobs, an increase of about 11 percent.

In the seven coastal counties running from York to Hancock, total employment grew even more rapidly, adding more than 80,000 jobs, an increase of more than 22 percent.

Over the last two decades, the rim counties’ share of total employment dropped from 19 percent to 16 percent. And just as importantly, their share of total earnings fell from 17 percent to 14 percent.

The average earnings per worker — meaning the total money earned from all jobs, full and part time, wage earners plus sole proprietors, divided by the total number of people working — rose from $20,802 in 1990 to $34,279 in 2010, an increase of 64 percent.

By comparison, the average earnings per worker in the central counties increased by 101 percent to $40,443 in 2010, and the average earnings per worker in the coastal counties increased by 124 percent to $42,669 over the same period.

In short, the income differential among Maine’s regions has increased.

In 1990, the average earnings of workers in the central counties was 8 percent higher than that of workers in the rim counties, and the average earnings of workers in the coastal counties was 12 percent higher.

By 2010, those differentials had grown to 18 percent more for workers in the central counties and 24 percent more for workers in the coastal counties.

Given these harsh economic trends, it is no wonder that the population of the rim counties declined by more than 9,000 people over the two-decade period, dropping from just over 272,000 in 1990 to just over 263,000 in 2010.

The population of the central region, in contrast, grew by more than 16,000, an increase of approximately 4 percent. And the population of the coastal counties grew by more than 93,000, an increase of nearly 16 percent. In 2010, the coastal counties accounted for more than half (51 percent) of Maine’s total population, up from 48 percent in 1990.

So what are we to do about this growing inequality?

The greatest immediate challenge is to find ways to prevent diseconomies of scale from accelerating economic decline.

In an environment of declining population, the unit cost of virtually everything rises. Schools with fewer students cost more on a per-student basis; hospitals with fewer patients cost more on a per-patient basis; town halls, fire and police stations, roads, libraries, public radio towers, virtually every element of public infrastructure becomes more expensive to operate as its pool of users declines.

As a natural consequence, the cost to taxpayers to maintain these pillars of community life increases, further pressuring the downward economic cycle.

The one area of infrastructure where this seemingly inescapable pattern of growing inefficiency does not apply is connection to the digital infrastructure of the Internet.

Yes, stringing wires down the “last mile” to every rural home and business is very expensive on a per-person basis. But once in place (by wire, tower or satellite), the opportunities for growing efficiency are virtually limitless. Students can interact with virtual teachers and classmates; hospitals can draw on equipment, facilities and people they could never afford to provide locally; town halls can provide assessing, dispatch, crime investigation, data collection and licensing/permitting services electronically.

Connecting rural Maine to the digital world of the 21st century could — if we do it creatively — have as large an impact as connecting it to the electronic world of the 1920s and 1930s.

Charles Lawton is senior economist for Planning Decisions, a public policy research firm. He can be reached at:

clawton@maine.rr.com