Description of fastfood dataset

Source: Card, David, and Alan B. Krueger. "Minimum Wages and Employment: A Case 
Study of the Fast-Food Industry in New Jersey and Pennsylvania." American 
Economic Review 84, no. 4 (1994): 772-793.

Original data available at: https://davidcard.berkeley.edu/data_sets.html

This is a slightly cleaned and restructured version of the original data, converted from 
long format (820 restaurant-period observations) to wide format (410 restaurant 
observations) for easier analysis. The original data 
are also available in R through the loedata package.

The dataset contains survey data from 410 fast-food restaurants in New Jersey 
and eastern Pennsylvania collected in two waves: February 1992 (before New 
Jersey's minimum wage increase) and November-December 1992 (after the increase). 
On April 1, 1992, New Jersey raised its minimum wage from $4.25 to $5.05 per 
hour, while Pennsylvania's minimum wage remained at $4.25. The data were used 
to estimate the causal effect of minimum wage increases on employment using a 
difference-in-differences design.

Sample: Fast-food restaurants (Burger King, KFC, Roy Rogers, Wendys) in New 
Jersey and eastern Pennsylvania

Number of observations: 410 restaurants (820 restaurant-period observations in 
the original long format)

Variables:

Identifiers:
id -- Unique restaurant identifier created for wide format
sheet -- Original sheet number from Card and Krueger's survey (unique store ID)

Treatment Variables:
state -- Factor variable indicating state: "Pennsylvania" (control) or 
         "New Jersey" (treatment). New Jersey experienced the minimum wage 
         increase; Pennsylvania did not.
location -- Factor variable indicating geographic region within state: 
            "NJ_South", "NJ_Central", "NJ_North", "NJ_Shore" for New Jersey 
            restaurants; "PA_PhillyNE" (northeast suburbs of Philadelphia) or 
            "PA_Easton" for Pennsylvania restaurants

Restaurant Characteristics:
chain_name -- Factor variable indicating restaurant chain: "Burger King", "KFC", 
              "Roy Rogers", or "Wendys"
ownership -- Factor variable indicating ownership type: "Franchise" or "Company" 
             owned

Pre-Treatment Variables (February 1992):
wage_st_pre -- Starting wage for new employees in dollars per hour
wage_gap -- Amount by which the pre-treatment starting wage was below the new 
            $5.05 minimum (computed as max(5.05 - wage_st_pre, 0)). Positive 
            values indicate restaurants that were legally required to raise wages.
fte_pre -- Full-time equivalent employment, computed as empft_pre + nmgrs_pre + 
           0.5*emppt_pre
empft_pre -- Number of full-time employees
emppt_pre -- Number of part-time employees
nmgrs_pre -- Number of managers and assistant managers
pctaff_pre -- Percentage of employees affected by the new minimum wage (i.e., 
              earning below $5.05)
hrsopen_pre -- Number of hours restaurant was open per day
inctime_pre -- Typical time (in months) until first raise for new employees
firstinc_pre -- Typical amount of first raise in dollars per hour
bonus_pre -- Binary indicator equal to 1 if restaurant offered cash bonus for 
             recruiting new workers
meals_pre -- Numeric code for meal benefits: 0=none, 1=free meals, 2=reduced 
             price meals, 3=both free and reduced price
open_pre -- Hour of opening (e.g., 6.5 = 6:30 AM)
psoda_pre -- Price of medium soda including tax (dollars)
pfry_pre -- Price of small fries including tax (dollars)
pentree_pre -- Price of entree including tax (dollars)
nregs_pre -- Number of cash registers in store
nregs11_pre -- Number of registers open at 11:00 AM

Post-Treatment Variables (November-December 1992):
wage_st_post -- Starting wage for new employees in dollars per hour
fte_post -- Full-time equivalent employment
empft_post -- Number of full-time employees
emppt_post -- Number of part-time employees
nmgrs_post -- Number of managers and assistant managers
hrsopen_post -- Number of hours restaurant was open per day
inctime_post -- Typical time (in months) until first raise for new employees
firstinc_post -- Typical amount of first raise in dollars per hour
bonus_post -- Binary indicator for cash bonus for recruiting new workers
pctaff_post -- Percentage of employees affected by the new minimum wage
meals_post -- Numeric code for meal benefits
open_post -- Hour of opening
psoda_post -- Price of medium soda including tax (dollars)
pfry_post -- Price of small fries including tax (dollars)
pentree_post -- Price of entree including tax (dollars)
nregs_post -- Number of cash registers in store
nregs11_post -- Number of registers open at 11:00 AM

Change Variables (Post minus Pre):
dfte -- Change in full-time equivalent employment (fte_post - fte_pre). This is 
        the primary outcome variable for difference-in-differences estimation.
dwage -- Change in starting wage (wage_st_post - wage_st_pre)

Data Quality Variables:
balanced -- Binary indicator equal to 1 if the restaurant has complete employment 
            data (empft, emppt, nmgrs) in both survey waves, 0 otherwise. Card 
            and Krueger's main analyses use balanced=1.
ncalls -- Number of call-backs required to complete the second survey
status2 -- Status of second interview (see Card and Krueger documentation)
date2 -- Date of second interview in MMDDYY format
type2 -- Type of second interview: 1=phone, 2=personal

Note: Some restaurants have missing data for key variables (wage_st_pre, 
wage_st_post, employment measures), typically due to survey non-response or 
restaurant closure. The balanced variable identifies restaurants with complete 
employment data suitable for difference-in-differences analysis.