Now that we have the option, it's time to consider which dayparting tactics and strategies make the most sense for any given campaign.  For example, Google recommends that some advertisers may want to schedule their ads to run only during business hours, and others may want to raise maximum bids during high-traffic times of the day (lunchtime, for example, is typically a time of higher-than-average consumer purchases).  At first glance this seems logical enough, but will this truly contribute to overall campaign efficiency? Based on what I've seen, not necessarily. 

Taking a look at three months worth of data representing campaigns across three different industries (retail, financial and travel) and sliced click and conversion data by the hour of the day (EST), here are some findings:

NOTE: Each campaign did not utilize any dayparting; campaigns were set to deliver evenly across the day.

• All three campaigns saw vastly less click activity after 11p.m.  OK, this is fairly instinctual--but this trend likely isn't happening for the reasons you may think.  More on this below, but it should also be noted that in turn, these hours also saw the poorest conversion rates and highest cost-per-acquisitions of our sampling.

• Also after 11pm, all three of our analyzed campaigns saw a sharp spike in their assessed cost-per-click fees.  This likely resulted from AdWords' Daily Budgeting feature rather than the effects of dayparting, but is rather interesting nonetheless.  Consider it this way: as each day begins, the daily budgets of all advertisers start anew.  As the day progresses, those advertisers with smaller budgets gradually begin to disappear from the bidding process, leaving the remaining advertisers paying far less for each click (which was noticed across all three of these campaigns).  Conversely, when budgets are then restored at the end of the day, many advertisers will see their cost-per-clicks soar, as they now have to outbid several additional listings.  This certainly won't affect all AdWords users, but those with high maximum bids should certainly be aware of this possibility. 

• It seems the most advantageous conversion rates and cost-per-acquisition numbers stemmed from the early evening hours (between 7 p.m. and 11 p.m. specifically).  This directly contradicts a common pay-per-click mentality that ads running during standard business hours are the most ROI-efficient; this was once believed to be the time to best catch the most Internet users at their computer and in the "marketing mindset." However, from a pure ROI perspective, it appears this may not be the case.

While I certainly can't promise that the above will be the case for ALL AdWords campaigns, it stands to reason that other advertisers may very well see a similar performance within their own accounts. 

So assuming you are running an ROI-focused campaign (and aren't a multibillion-dollar campaign burning thousands upon thousands of dollars a day fishing for raw traffic), maybe we can come up with some general dayparting "best practices" of sorts. 

• Daypart early. As we've seen above, clicks can suddenly become quite expensive after midnight once daily budgets start anew.  Given how we've seen conversion rates plummet at this time, it would probably make sense to daypart around these hours.

• Know Your CPC and CPA. Even if you notice good conversion rates for certain hours, take a look at CPCs and CPAs to make sure you're making the best possible use of these funds (i.e., would they be a greater contributor to campaign ROI if spent during more advantageous hours).

• Unique Ad Groups. If you have a particular group of keywords that is important to your organization (from a revenue perspective or otherwise), consider taking these terms and mirroring them in an additional unique ad group.  The idea would be to use this ad group to run on campaign "off hours," with bids configured to make the most sense from an ROI and CPC perspective.

• Test. Perhaps most important, test, test and then test some more! There's a litany of different factors that affect specific campaigns in radically different numbers. Isolate each variable in its own test group and find out what's working for you--and what's working not-so-well.

I urge everyone to check archived data from their own pay-per-click efforts, within AdWords and other campaign engines as well, and see if these findings are consistent across the board.