If it seems the inventory of hair color products on Island drugstore and supermarket shelves is growing larger every year - well, it probably is. New data released by the U.S. Census Bureau this week shows that gray hair is the increasingly predominant theme in Dukes County, and for that matter all over Massachusetts, as the population grows older and the number of households with children begins to dwindle.

Countywide, the median age is up, from just over 37 years a decade ago to just over 40 in 2000. Statewide, the median age was 36 in 2000, up from 33.6 in 1990. Median age means that exactly half the population is above that age and half the population is below. On Cape Cod, the median age also went up in the last decade, from 39.5 to 44.6.

On the Vineyard, Chilmark is the oldest town, with a median age of 45.6 years, and Aquinnah is the youngest, with a median age of 37.1. In Edgartown the median age was 40.3 in 2000, in West Tisbury the median age was 41.1. In Tisbury the median age was 42 and in Oak Bluffs the median age was 39.4.

The Census Bureau released general demographic profile information for Massachusetts on Tuesday of this week. The profile includes information on age, sex, race and housing for the population, both for the commonwealth and for towns and counties.

In Dukes County, the biggest population increase over the last 10 years took place among people who are 35 to 54 years old. In 1990 there were 3,452 people in that age bracket; in 2000 there were 5,482 people in the same age bracket, an increase of 58 per cent.

Countywide, the number of infants and toddlers from birth to age four dropped slightly, from 826 in 1990 to 817 in 2000. So did the population age group that includes their parents - the 20 to 34-year-old age group declined by 2,424 to 2,303 over a 10-year period. The shrinking young adult population in Dukes County mirrors the rest of New England, where there is now concern that the decline in the 20 to 35-year-old age group may threaten to slow the regional economy.

Young adults today are considered part of what is termed the "baby bust" generation, born during a period when inflation and the oil crisis triggered a low birth rate throughout New England.

But Dukes County still has plenty of children in the 5 to 14 age bracket. The population of children aged 5 to 9 went up from 813 to 889, and the population of children aged 10 to 14 grew from 678 in 1990 to 1,077 in 1000. The Martha's Vineyard Regional High School is bracing itself to meet the challenge of educating this age group, which is expected to push enrollment beyond capacity for the next several years. Conversely, the elementary schools are expected to see enrollments drop.

Countywide, the 15 to 19-year-old-age group increased from 562 in 1990 to 882 in 2000.

Older age groups saw slight increases in the last 10 years. In Dukes County, the number of people 55 to 59 years old increased from 493 in 1990 to 829 in 2000.

Household information for Dukes County followed some of the same patterns as the state, but not in every area.

The biggest difference is in total occupied housing units. Statewide, 93 per cent of some 2.6 million housing units were occupied in the year 2000. But in the seven resort towns of Dukes County, vacant housing units actually outnumbered occupied housing - 43.3 per cent of the housing units were occupied in 2000, while 56.7 per cent were counted as vacant. In Dukes County the total number of 14,836 housing units nearly matched the total population of 15,007.

The percentage of households headed by single women in Dukes County was somewhat lower than the percentage statewide - countywide, 9.8 per cent of the households were headed by females with no husband present, while statewide 11.9 per cent of households were headed by women alone.

Women outnumber men in Dukes County and also in Massachusetts. Countywide last year, the total male population was 7,323, while the total female population was 7,664.

Only two towns in the county broke the state and county pattern for gender - Edgartown, where the Census Bureau counted 1,867 women and 1,912 men, and Gosnold, where 50 men and 36 women were counted.

The average household size in Dukes County was 2.3 people in 2000 and the average family size was 2.9 people.

The Census Bureau counted 2,915 married couples in Dukes County in 2000, and 1,295 married couples with children.