Introduction to Stata and DASP

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1 Introduction to Stata and DASP Abdelkrim Araar, Sami Bibi and Jean-Yves Duclos Workshop on poverty and social impact analysis Dakar, Senegal, June 2010 Introduction to Stata and DASP PEP and UNDP June / 24

2 Outline Introduction to Stata DASP: a Stata package for distributive analysis Conclusion Introduction to Stata and DASP PEP and UNDP June / 24

3 Objectives Understand the basic structure of the Stata software; Discover Stata s various elements of graphical interface; Understand how DASP can be useful for the analysis of distributions of welfare; See the basic structure of DASP modules; Consider the challenges and the difficulties of measuring poverty and welfare in a money-metric framework; See how the information required by DASP is related to important issues in welfare economics; See how to generate tabular and graphical output with DASP Introduction to Stata and DASP PEP and UNDP June / 24

4 Outline Objectives Introduction to Stata Stata in few words Main Stata graphical interfaces Main Stata graphical interfaces Dialog box and Stata commands Introduction to Stata DASP: a Stata package for distributive analysis Conclusion Introduction to Stata and DASP PEP and UNDP June / 24

5 Stata in few words Stata is a statistical software used by several firms and academic institutions throughout the world. Stata allows, inter alia, to process data; perform statistical analysis; draw graphs; make statistical simulations; design specialized and complementary programs; Stata has become increasingly popular during the last years. This can be explained in part by its optimized design and its simple graphical interface. Introduction to Stata and DASP PEP and UNDP June / 24

6 Main Stata graphical interfaces Introduction to Stata and DASP PEP and UNDP June / 24

7 Main Stata graphical interfaces A The commands window This allows typing a Stata command line and executing it by entering the Enter button. Page-Up: to edit the preceding command. Page-Down: to edit the successive command. Tab: to complete the name of the variable. Introduction to Stata and DASP PEP and UNDP June / 24

8 Main Stata graphical interfaces B The review commands window This window displays the last few lines typed and executed in the commands window. Click once on a given command line that appears in this window to copy it in the commands window; Click twice on a given command line that appears in this window to execute it; Clicking on the left button of the mouse shows a menu that allows you to copy or save the commands used during the session in a *.do file. Introduction to Stata and DASP PEP and UNDP June / 24

9 Main Stata graphical interfaces C The variables window This window lists the names of the variables of the opened data file as well as their label names and format. Click once on a given variable to copy it in the commands window; Clicking on the left button of the mouse shows a menu that allows you to rename variables or add some notes on the current data file. Introduction to Stata and DASP PEP and UNDP June / 24

10 Main Stata graphical interfaces D The results window This window displays the results of the submitted Stata commands. Select part or the whole set of results and click on the left button of the mouse to copy that in text or tabulated format. Introduction to Stata and DASP PEP and UNDP June / 24

11 Dialog box and Stata commands Stata s main menu also contains other items to access the dialogue boxes. Dialogue boxes facilitate learning the syntax of Stata commands. To execute commands, Stata offers three possibilities: 1. Typing the command in the commands window and clicking on Entrer; 2. Executing the Stata command in a dialog box; 3. Executing a *.do file (an ASCII text file that contains a set of successive Stata command lines). Introduction to Stata and DASP PEP and UNDP June / 24

12 Dialog box and Stata commands To display the dialog box of a command, two options are available. The first is to select the command item from Stata s main menu Example: Main Menu: Statistics Summaries Summary statistics Summary statistics The second is to type the command db followed by the command of interest and then click on Entrer. Example db summarize Introduction to Stata and DASP PEP and UNDP June / 24

13 Dialog box and Stata commands Figure 1: Dialog box of the Summarize command Introduction to Stata and DASP PEP and UNDP June / 24

14 Dialog box and Stata commands Display the help for the command Reset: Initialize the dialog box fields by their default values. Copy in clipboard the syntax that will be generated after clicking on OK Execute the command and close the dialog box Close the dialog box. Execute the command without closing the dialog box. This button is useful when we plan to explore the command with different options. Introduction to Stata and DASP PEP and UNDP June / 24

15 Dialog box and Stata commands By clicking on Submit or on OK, the generated command appears automatically in the commands window. Each of the three forms of execution has its specific usefulness. 1. The use of dialog boxes generates an accurate Stata syntax when options are selected. This helps learn quickly Stata s command syntax. 2. A do file may contain a set of command lines that can form an entire program. Users can save this to reuse it and modify at their later convenience. 3. More advanced Stata users can use directly the commands window to generate quickly some statistical results. Introduction to Stata and DASP PEP and UNDP June / 24

16 Outline Objectives Introduction to Stata DASP: a Stata package for distributive analysis DASP in few words DASP features Other DASP features DASP s main menu DASP s main variables Using variables in DASP Inputting DASP commands Applications and files in DASP Producing curves with DASP Saving DASP graphs DASP: a Stata package for distributive analysis Conclusion Introduction to Stata and DASP PEP and UNDP June / 24

17 DASP in few words Stata enables programmers to provide specialized.ado routines to add to the power of the software. DASP, which stands for Distributive Analysis Stata Package, is mainly designed to assist researchers and policy analysts interested in conducting distributive analysis with Stata. DASP uses Stata for two main reasons: Stata is a powerful tool to store and manage household data surveys. Combining DASP and Stata allows to use the same environment for processing and analyzing data. Stata easily allows adding specialized programs, making it possible for programmers to add to its power and flexibility. Introduction to Stata and DASP PEP and UNDP June / 24

18 DASP features DASP allows to: Estimate the most popular statistics (indices, curves) used for the analysis of poverty, inequality, social welfare, and equity; Estimate the differences in such statistics; Estimate standard errors and confidence intervals by taking full account of survey design; Perform the most popular distributive decomposition procedures; Check for the ethical robustness of distributive comparisons; Support distributive analysis on more than one data base at the same time. Introduction to Stata and DASP PEP and UNDP June / 24

19 Other DASP features Contains optimized algorithms for the estimation of distributive indices; Unifies syntax and parameter use across various estimation procedures for distributive analysis. For each DASP module, three types of files are provided 1 : *.ado file: contains the program of the module. *.hlp file: contains the help material for the given module. *.dlg file: allows the user to perform the estimation using the module s dialog box. 1 For more information about DASP modules, see the user manual: (Araar and Duclos (2007)). Introduction to Stata and DASP PEP and UNDP June / 24

20 DASP s main menu DASP s windows menu makes it possible to access quickly each of the dialog boxes. The latter are grouped by main themes. Introduction to Stata and DASP PEP and UNDP June / 24

21 DASP s main variables VARIABLE OF INTEREST. This is the variable that usually captures living standards. It can represent, for instance, income per capita or expenditures per adult equivalent. SIZE VARIABLE. This refers to the ethical or physical size of the observation. This variable usually refers to the number of household members. GROUP VARIABLE. Say that we wish to estimate poverty within a country s rural area or within female-headed families. One way to do this is to force DASP to focus on a population subgroup defined as those for whom some GROUP VARIABLE(say, area of residence) equals a given GROUP NUMBER (say 2, for rural area). SAMPLING WEIGHT. Sampling weights are the inverse of the sampling probability. This variable should be set upon the initialization of the data set. Introduction to Stata and DASP PEP and UNDP June / 24

22 Using variables in DASP DASP makes it possible to use simultaneously more than one data file. The user should initialize each data file before using it with DASP. This initialization is done by: Labeling variables and values for categorical variables; Initializing the sampling design with the command svyset; Saving the initialized data file. It is useful to add a character such as I to the names of initialized files (Example: Uganda99I.dta) in order to distinguish them. Introduction to Stata and DASP PEP and UNDP June / 24

23 Inputting DASP commands Stata and DASP commands can be entered directly into a command window: An alternative is to use dialog boxes. For this, the command db should be typed and followed by the name of the relevant DASP module. Example: db ifgt. Introduction to Stata and DASP PEP and UNDP June / 24

24 Applications and files in DASP Two main types of applications are provided in DASP. For the first one, the estimation procedure uses only one data file, the data file in memory (or loaded ). It is from that file that the relevant variables must be specified. Introduction to Stata and DASP PEP and UNDP June / 24

25 Applications and files in DASP Two main types of applications are provided in DASP. For the second type of applications, two distributions are needed. For each of these two distributions, the user can specify the currently-loaded data file (the one in memory) or one saved on disk. Introduction to Stata and DASP PEP and UNDP June / 24

26 Producing curves with DASP DASP was strongly designed to facilitate the of use curves to display distributive information. For instance, if we wish to graph Lorenz curves to compare inequality between rural and urban areas, we can simply type the following command line: clorenz exppc, hgroup(zone) hsize(size) where in this example exppc is per capita expenditures, size is household size and zone is the zone variable (1 = rural / 2= urban). Introduction to Stata and DASP PEP and UNDP June / 24

27 Producing curves with DASP After executing this command the following windows appears: Introduction to Stata and DASP PEP and UNDP June / 24

28 Producing curves with DASP For many curves, DASP allows showing their confidence intervals according to selected levels of statistical significance (this value is by default set to 95%). For instance, to draw confidence intervals around FGT curves, we can use the cfgtsm DASP module. cfgtsm exppc, alpha(0) hsize(size) hgroup(sex) max(100000) Introduction to Stata and DASP PEP and UNDP June / 24

29 Producing curves with DASP After executing this command the following windows appears: Drawing the confidence interval of distributive curves (FGT curves) Introduction to Stata and DASP PEP and UNDP June / 24

30 Saving DASP graphs Graphs produced with DASP or Stata can be saved in many different formats. Among them: *.gph *.wmf *.eps is Stata s graphical format. It is useful to allow re-editing the graph (with Stata 10 or higher). is the Windows metafile format. This format may be easily inserted into Word documents. The user can also copy a Stata graph and past it directly into a Word document. is the encapsulated postscript format. This format can easily be inserted in Latex documents. Introduction to Stata and DASP PEP and UNDP June / 24

31 Outline Objectives Introduction to Stata DASP: a Stata package for distributive analysis Conclusion Summary Relevant DASP commands Exercises with Stata and DASP Reference Conclusion Introduction to Stata and DASP PEP and UNDP June / 24

32 Summary Stata is a popular software that provides powerful statistical applications and that is simple to use. Stata commands can be inputted through dialog boxes, do files, or commands windows. DASP facilitates the estimation of the most popular statistics used for the analysis of poverty, inequality, social welfare, and equity, and provides various sophisticated statistical tools to check for the robustness and the precision of such statistics DASP unifies syntax and parameter use across various estimation procedures for distributive analysis. DASP allows the use of two distributions at the same time, and simplifies the production of tables and graphs. Introduction to Stata and DASP PEP and UNDP June / 24

33 Relevant DASP commands FGT and EDE-FGT poverty indices (ifgt). FGT CURVE with confidence interval (cfgts). Lorenz and concentration CURVES (clorenz). Introduction to Stata and DASP PEP and UNDP June / 24

34 Exercises with Stata and DASP Exercises 1.1, 1.2, 1.3 Introduction to Stata and DASP PEP and UNDP June / 24

35 Reference ARAAR, A. AND J.-Y. DUCLOS (2007): DASP: Distributive Analysis Stata Package, PEP, CIRPÉE and World Bank, Université Laval. Introduction to Stata and DASP PEP and UNDP June / 24

USER MANUAL. DASP version 2.3. DASP: Distributive Analysis Stata Package. Abdelkrim Araar, Jean Yves Duclos

USER MANUAL. DASP version 2.3. DASP: Distributive Analysis Stata Package. Abdelkrim Araar, Jean Yves Duclos USER MANUAL DASP version 2.3 DASP: Distributive Analysis Stata Package By Abdelkrim Araar, Jean Yves Duclos Université Laval PEP, CIRPÉE and World Bank June 2013 Table of contents Table of contents...