Q I read that the population in the United States is getting shorter, and I wonder why that is. Are Americans simply not growing as tall as before, or is the number going down because people of smaller stature from Mexico, Central and South America are coming here and affecting the overall pool?

A News that Americans are no longer the tallest people in the world probably was taken from research published last year in the Social Science Quarterly, according to Barbara Ronningen of the Minnesota State Demographic Center. Because the study focused on white and black non-Hispanic Americans, immigration you describe is not a factor.

Americans had been the tallest in the world for more than two centuries until World War II, according to study authors John Komlos and Benjamin E. Lauderdale. By the end of the 20th century, people in many European populations were taller. The height of Americans basically stagnated while that of Europeans increased.

The published report, "Underperformance in Affluence; The Remarkable Relative Decline in U.S. Heights in the Second Half of the 20th Century," also shows that only for those born between 1975 and 1983 is some height gain apparent in the United States, but that's among whites, not blacks. (For men and women, the relationship between height and income, and between height and educational attainment, has not changed appreciably over time.)

The report's authors speculate that the U.S. health-care system, as well as the relatively weak welfare safety net, might be why human growth in the United States has not performed as well in relative terms as one would expect on the basis of income alone. The results bear some similarity to studies of life expectancy, which also show the United States lagging Europe.

Gummy furniture

Q I have furniture I have been polishing for about 60 years. The tops of the dining room chair backs are sticky from people's hands. What can be done about that?

A It sounds as though the finish has degraded from an accumulation of wax and polish applied over the years. If that's the case, there's not much you can do.

Try washing with a mild soap, such as Murphy's Oil Soap, and then dry. Be careful not to scrub because that may remove the finish, which is probably now bound to the wax.

The other option is to refinish the wood. You can do that yourself, of course, but it's a big job. You might want to talk with a professional first.

Send your questions to Fixit in care of the Star Tribune, 425 Portland Av. S., Minneapolis, MN 55488, or call 612-673-9033, or e-mail fixit@startribune.com. Past columns are available at www.startribune.com/fixit. Sorry, Fixit cannot supply individual replies.