It's hard to believe that the "first significant page" on Google is its "about" page: //www.google.com/intl/en/about.html, which you have to click on to get to the privacy policy introduction, before you can get to the actual privacy policy.
The latter vertical line, on the other hand, is on 2008, belonging to the year of policy introduction as well as the onset of the global economic crisis.
The double difference estimator is constructed by interacting the group indicator (G) with a single time dummy (P) that is equal to 1 for the whole period following the date of the policy introduction, and 0 for the whole period preceding the date of the policy introduction.
However, recent research has shown that the adoption of deployment policies carries the potential of locking in the technology that is most cost-effective at the point of policy introduction, but may be inefficient in the long term.
More specifically, there is no allowance for quarter and year specific dummies, and the comparison is between the entire period after the policy introduction and the entire period before the policy.
Monthly consumption of several antibiotics was monitored in defined daily doses (DDDs) per 1000 patient-occupied bed-days (1000 pt-bds) 24 months before (2012 2013) until 24 months after new antibiotic policy introduction (2014 2015).
The dummy variable P called the time indicator is by definition equal to 1 for the period following the date of the policy introduction (i.e. between 3 r d quarter of 2008 and 2 n d quarter of 2010), and 0 for the period preceding the date of the policy introduction (i.e. between 3 r d quarter of 2006 and 2 n d quarter of 2008).
The quarterly data allow distinguishing pre- and post-policy periods such that the policy period ranges from the third quarter of 2008 to the second quarter of 2010, while the period before the policy introduction is between the third quarter of 2006 and the second quarter of 2008.
The DDD estimation results, displayed in the bottom panel of Table 4, suggest that as for the most restricted specification which imposes constant policy effect across quarters, the probability of being hired for a woman aged 30 to 34 increased by 0.2% relative to a man of the same age group after the policy introduction.
Indeed, S1 is equal to 1 if year is 2008 and the period is after the policy introduction (i.e. third and fourth quarter), S2 is equal to 1 if year is 2009 and S3 is equal to 1 if year is 2010 and the period is until the end of the policy period (i.e. the first and second quarter).
