Slowing search query phrase length growth

I've seen OneStat.com search query length trend data on a couple occasions previously (June ’04 and August ’05); in both previous cases the trends were clearly positive for the search engines. I just saw July '06 year-over-year data from OneStat, though, and I see clouds building in terms of intrinsic query value; the rate of growth of longer phrase queries has started to slow for the first time ever. Below is a breakdown of absolute growth or decline in queries of different lengths over the last 3 years:

Length '03-'04 '04-'05 '05-'06 (all %'s are Y/Y and absolute)
1 Word (23.2%) (19.2%) (14.8%)
2 Word 11.5% (1.6%) (2.3%)
3 Word 5.3% 2.7% 1.0%
4 Word 4.0% 9.3% 5.6% (deceleration in '05-'06 growth)
5 Word 3.9% 12.1% 8.8% (deceleration in '05-'06 growth)
6 Word 5.0% 14.2% 14.6% (growth rate unchanged '05-'06)
7 Word 4.3% 18.6% 18.7% (growth rate unchanged '05-'06)

[Sorry for the crappy formatting, I'm hopeless]

Keyword phrase length is one of the most important metrics to track, as it is a leading indicator for search monetization. Better defined searches convert better than 1 or 2 word search phrases, and therefore advertisers are willing to pay more for longer keyword searches. The above data, then, is telling us that the search engines’ inventory is not going to continue increasing in value to the extent it has previously. Our message to the market; if the value of queries starts to level off, better optimization becomes all the more important.