> So what I need to do is add all the previous months of December to the
> current month of December:

that would just be <xsl:value-of select="sum(preceding-sibling::year/month[@month='December']/@percentage-increase)"/>

But it sounds like you want a product, not a sum????

> The first year (1937) increases only 103 percent from the previous year.
> 
> The next year (1938)shows an increase of 102 percent from 1937. But
> cumalitively it shows an increase of 105 percent: 103 + 102 = 105.
> 
> The next year (1939)  shows an increae of 108 percent. Cumulatively,
> this is 113: 103 + 102 + 108 = 113.

cumulative interest isn't additive
The increase over three years is 1.03 * 1.02 * 1.08 =~ 1.135 or 13.5%
so you will need a recursive template as xpath2 doesn't have a product
built in (or you could use saxon7's implementation of xpath 2 draft,
which does)

David


-- 
http://www.dcarlisle.demon.co.uk/matthew

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list