trying to find up to date statistics for u.s. on age differences in
relationships. I want something clear and simple like you would see in
cosmo, example .....10 percent age same or 2-3 year difference, 15
percent age diff 4-6 years ect.......

Hello.

From the U.S. Census Bureau:

                                              Married couples
Male 6 or more years older than female        19.6 %
Male 2 to 5 years older than female           36.3 %
Within 1 year of each other                   31.8 %
Female 2 to 5 years older than male            9.0 %
Female 6 or more years older than male         3.3 %

                                              Unmarried couples
Male 6 or more years older than female        24.7 %
Male 2 to 5 years older than female           28.6 %
Within 1 year of each other                   25.5 %
Female 2 to 5 years older than male           12.0 %
Female 6 or more years older than male         9.1 %

Source: Table 8, page 15, "America's Family & Living Arrangements
2000"
US Census Bureau, 2001 publications 
http://www.census.gov/prod/2001pubs/p20-537.pdf
(PDF format, so the Adobe Acrobat Reader is required. If you don't 
have that, visit Adobe's web site: 
http://www.adobe.com/products/acrobat/readstep2.html )  

Now, if you want to express the data above in a gender-neutral way,
you could simply add the respective categories. For example, you could
say that among unmarried couples, 33.8% have an age difference of 6
years or more (i.e., you'd add the top 24.7% to the bottom 9.1%
figure). This would give all of the unmarried couples that have an age
difference of 6 years or more. Similarly you could say that 40.6% of
unmarried couples have an age difference of 2 to 5 years (i.e., you'd
add the 28.6% figure to the 12.0% figure).
 


There's some slightly different, older data in a 1999 article
entitled, "Age Differences Between Sexual Partners In the United
States."

From that report:

Among women 15-44:
10 % - boyfriend/husband 3 or more years younger
52 % - boyfriend/husband within two years younger or older
20 % - boyfriend/husband 3-5 years older
18 % - boyfriend/husband 6 or more years older
Source:
"Age Differences Between Sexual Partners In the United States"
By Jacqueline E. Darroch, David J. Landry and Selene Oslak 
Hosted by agi-usa.org (see site for additional statistics)
http://www.agi-usa.org/pubs/journals/3116099.html

search strategy: "age differences", couples, "years older than",
"years younger than"

I hope this helps.

i dont think people should worry about age differences

This is an interesting reading about some mathematical models which
correlate income and age at marriage.

http://www.econ.lsa.umich.edu/wpweb/1992/92-10.pdf

Abstract:

This paper provides an empirical investigation of a theoretical model
of the marriage market. In the model, women are valued more for their
ability to bear children and men are valued more for their ability to
make money. Men cannot reveal their labor market ability to potential
spouses until they enter the labor force. At the same time, the
relevant information for evaluating females as spouses is revealed at
a younger age. The model predicts that the income of males will be
positively associated with age-at-first-marriage. We find empirical
support for the model. However, we also find the association between
male earnings and age-at-first-marriage becomes negative for those who
married after age 30, which was not predicted by the model. Consistent
with the model, we do not find a strong relationship between earnings
and age-at-first-marriage among females.

From this paper, we could easily conclude that age differences might
be important in the economic stability of the marriage.

I remember a note, by Pollux, a researcher in this field, who says
that an old man can be more attractive than an equally rich but
younger man, based on another mathematical model.

I also remember that some researches had associated schizophrenia in
the offspring with older fathers. (There are other hypothesis about
schizophrenia, and it's only in part genetic.) Down syndrome, (and
other diseases), in the offspring are associated with older mothers.

Basically, the older the parent, the higher the chances are that a
mutation has occured in ther seeds.

While this is not related directly to the question, it's clear that
indirectly, age at marriage, (and thus difference age too), might have
an importance in marriage. How big this importance is it's something I
can't tell by now.