Final answer:
The exact percentage of private label grocery store purchases in July 2009 is not provided in the text, but the Bureau of Labor Statistics' Consumer Expenditure Survey indicates a decline in total food spending in the U.S. during that period.
Step-by-step explanation:
The question regarding the percentage of grocery store purchases in July 2009 that were of private labels (store brand) in North America requires specific market research data from that time period. However, the provided text does not give this particular statistic. Instead, the text focuses on a universal increase in spending in a certain category during tough economic times, noting an 18% uptick in the United States. The Bureau of Labor Statistics' Consumer Expenditure Survey indicated that "real total food spending by U.S. households declined five percent between 2006 and 2009," suggesting that the increase in spending was not related to groceries. To accurately answer the question about the percentage of private label purchases in grocery stores, one would need to look at specific market research reports from July 2009.