An analysis of debit card spending by members of participating credit unions showed they largely split their spending between Thanksgiving and the day after Thanksgiving.

The analysis, conducted by CO-OP Financial Services and Saylent Technologies, found that shoppers who belong to credit unions recorded roughly the same buying activity on Black Friday in 2012 as they did in 2011.

However, they dramatically increased their transaction and spending levels on Thanksgiving Day 2012 compared to the previous year. This year, a number of major national retailers opened on Thursday evening.

The analysis found that Black Friday transactions by credit union debit card holders actually decreased by 0.2%, and total dollars spent decreased 3.5%, in 2012 compared to 2011.

In a similar survey conducted last year, CO-OP and Saylent found that shoppers made 10.1% more transactions and spent 8.1% more during Black Friday in 2011 than in 2010.

But it was a much different story on Thanksgiving Day. Transactions increased 18.8%, and dollars spent increased by an even greater amount, 30.7%, in 2012 compared to the year prior.

For the entire two day period of Nov. 22-23, 2012, total transactions and dollars spent rose modestly year over year – a 6.25% rise in transactions, and a 6.5% rise in dollars spent.

This unique analysis of sales is not an estimate, but is based on more than 5.1 million actual transactions made on Thanksgiving Day and Black Friday, CO-OP said.