For those of us who are demographic buffs, Christmas came four days early this year when Census Bureau director Robert Groves announced yesterday the first results of the 2010 Census and the reapportionment of House seats (and thus, electoral votes) among the states.

The resident population of the United States, he said in a webcast, was 308,745,538. That’s an increase of 9.7 percent from the 281,421,906 in the 2000 Census — the smallest proportional increase than in any decade other than the Depression-era 1930s, but a pretty robust increase for an advanced nation.

First, the great engine of growth in America is not the Northeast megalopolis, which was growing faster than average in the mid-20th century, or California, which grew lustily in the succeeding half-century. It is Texas.

Its population grew 21 percent in the last decade, from nearly 21 million to more than 25 million. That was more rapid growth than in any states except for four much smaller ones (Nevada, Arizona, Utah, and Idaho).

Texas’s diversified economy, business-friendly regulations, and low taxes have attracted not only immigrants but substantial inflow from the other 49 states. As a result, the 2010 reapportionment gives Texas four additional House seats. In contrast, California gets no new House seats for the first time since it was admitted to the Union in 1850.

There’s a similar lesson in the fact that Florida gains two seats in the reapportionment and New York loses two.

This leads to a second point, which is that growth tends to be stronger where taxes are lower. Seven of the nine states that do not levy an income tax grew faster than the national average. The other two, South Dakota and New Hampshire, had the fastest growth in their regions, the Midwest and New England.

Altogether, 35 percent of the nation’s total population growth occurred in these nine non-taxing states, which accounted for just 19 percent of total population at the beginning of the decade.

My third observation is that immigration is slowing down and may be reversed. Immigration accelerated during the 1990s, and the 2000 Census showed more immigrants than the Census Bureau had estimated.

In contrast, immigration has clearly slowed down since the housing bubble burst and the construction industry went bust in 2007. And the 2010 Census showed fewer residents in several high-immigration states than the Census Bureau had estimated were there in 2009.

The drop was particularly big — 3 percent — in Arizona, where state and local governments have cracked down on illegals, notably by requiring employers to use the E-Verify system to determine immigration status (that law was signed by Janet Napolitano, then governor and now homeland-security secretary).

We can’t be sure before the release of more detailed data, but it looks as if we’re seeing significant reverse migration. The lesson is that states’ public policy and law-enforcement practices can make a difference.