Hospitality (tourism) also rose, by 2.9 percent, as did electricity consumption a scant 0.3 percent.
At the same time, month-to-month Humboldt County home sales dropped 9.5 as rising interest rates and other factors hindered real estate. Seasonally-adjusted sales plunged an extraordinary 25 percent from May 2005 to May 2006.
However, the drop in real (inflation-adjusted) home prices in the period was about 0.6 percent, and sales are forecast to remain stagnant until real prices come down substantially more.
The county's median home price is estimated at $319,000.
The big 18 percent gain in lumber returns that manufacturing index to the level it posted near the end of 2005, but it still remains well off the peak, the monthly report said.
The retail surge is the strongest performance of that sector in several months, and continues a long-term trend. Retail has risen 46 percent since the composite index was instituted at the start of 1994.
The Index of Economic Activity consists of data compiled by HSU's Department of Economics that are drawn from local businesses and organizations. Using January 1994 as the base month, the data are adjusted seasonally in a weighted combination of six individual sectors of the local economy that measure near-tern developments and long-term trends.