Hi

I am new to the Stata forum so apologies if this question has been asked before. I have panel data on individual taxpayers who were enrolled in an electronic lodgment service that was introduced in 1999 as a pilot. The e-lodgment was expanded over the years to cover some 2.6m taxpayers by 2011. Starting in 2003 the e-lodgment also incorporated prefilled data for taxpayers to reduce the compliance cost and make it easier to file tax returns. Compliacting the study is the fact that the number of labels (information) being prefilled also increased over the years (from 1 label in 2003 to 21 labels in 2008 and ) while the enrollment in the e-lodgment service was being expanded.

I am specifically trying to isolate the impact of prefilling on the individual tax return labels and am planning to use a difference-in-difference approach. I have data on a control group that did not use the e-lodgment system (and consequently did not use prefilling). However, I have not come across any research that uses DiD approach to study a program where coverage increases over time and the intensity of the treatment also changes. Would really appreciate if I could use the wisdom of the crowd to identify similar research.

My fallback option is to study a group of taxpayers that did not use e-lodgement until 2011 (when all the available information was prefilled meaning the treatment was not changing) and compare that with a control that did not use e-lodgment in 2010 and in 2011 using a DiD approach.

Many thanks in advance.