Tommy has recently graduated from SUSS and has joined a well-known retailer that operates 3 department stores in Singapore. His job function is that of a business analyst. It has been well-reported that retail business in Singapore is on the decline and his employer would like to determine if the forecast for the next few years will be equally bad. Tommy has been tasked to perform the analysis and his output will provide insights in the companys hiring and expansion plan in Singapore. The first thing Tommy did was to download the Retail Sales Index data from the Department of Statistics Singapore website. He specifically extracted the data for Department Stores from Q1 2008 to Q4 2018. (2017 is set as the base year with Index = 100). Refer to file: BUS107_GBA_RSIData.xls.

Use the techniques of time series modelling and with justifications, discuss the considerations on how Tommy would forecast the quarterly Retail Sales Index in 2019 and 2020.

Year/Quarter	Retail Sales Index (Department Stores)
2008 1Q	92.4
2008 2Q	93
2008 3Q	84.9
2008 4Q	105.3
2009 1Q	87.1
2009 2Q	88.6
2009 3Q	83.2
2009 4Q	103.6
2010 1Q	94.3
2010 2Q	93.9
2010 3Q	90.7
2010 4Q	109.3
2011 1Q	99.6
2011 2Q	99
2011 3Q	95.8
2011 4Q	119.3
2012 1Q	104.9
2012 2Q	99.9
2012 3Q	95
2012 4Q	117
2013 1Q	106.1
2013 2Q	100.9
2013 3Q	97.5
2013 4Q	118.6
2014 1Q	107.1
2014 2Q	98.7
2014 3Q	95.7
2014 4Q	117.6
2015 1Q	108.2
2015 2Q	101.1
2015 3Q	98.8
2015 4Q	114.4
2016 1Q	103.8
2016 2Q	93.9
2016 3Q	93.2
2016 4Q	112.9
2017 1Q	100.3
2017 2Q	93
2017 3Q	94.6
2017 4Q	112.1
2018 1Q	102.7
2018 2Q	92.3
2018 3Q	93.6
2018 4Q	112.8