TEJ Quarterly Financial Data: 2010 Q1 to 2026 Q2

1. Objective
2. Load the data
3. Variables
4. Coverage
5. Sample observations
6. Missing values
7. Duplicate company-quarter observations
8. Example: TSMC (stock ID 2330)
9. Data limitations and interpretation
10. Conclusion

1. Objective

This report organizes quarterly financial information obtained from the Taiwan Economic Journal (TEJ) for the period 2010 Q1 to 2026 Q2. The requested measures are total equity (book value), market value of common stock, and quarterly net operating income. The measures are total monetary amounts, not per-share values. Original export units are retained.

2. Load the data

# Read the processed TEJ export from the same folder as this .Rmd file.
financial_data <- read.csv(
  "TEJ_HW5_final.csv",
  colClasses = c(stock_id = "character"),
  na.strings = c("", "NA"),
  stringsAsFactors = FALSE
)

# Check the number of rows and columns.
dim(financial_data)

## [1] 131775      6

3. Variables

Field	Description
`stock_id`	Company/security identifier
`company_name`	Company name
`year_quarter`	Reporting quarter
`book_value_total_equity`	Total equity (book value)
`market_value_common_stock`	Market value of common stock
`operating_profit_quarter`	Estimated single-quarter operating income

4. Coverage

coverage <- data.frame(
  Measure = c("Observations", "Distinct stock IDs", "Distinct quarters", "First quarter", "Last quarter"),
  Value = c(
    nrow(financial_data),
    length(unique(financial_data$stock_id)),
    length(unique(financial_data$year_quarter)),
    min(financial_data$year_quarter),
    max(financial_data$year_quarter)
  )
)
knitr::kable(coverage)

Measure	Value
Observations	131775
Distinct stock IDs	2996
Distinct quarters	66
First quarter	2010Q1
Last quarter	2026Q2

5. Sample observations

To keep the published web page readable, only the first eight rows are displayed. The data file retains all observations.

knitr::kable(head(financial_data, 8))

stock_id	company_name	year_quarter	book_value_total_equity	market_value_common_stock	operating_profit_quarter
1101	TCC	2010Q1	102157504	98600641	2152334
1101	TCC	2010Q2	102349225	89876378	3791319
1101	TCC	2010Q3	109586305	109958645	4176068
1101	TCC	2010Q4	124513778	121103340	5534591
1101	TCC	2011Q1	128728151	131072213	3425462
1101	TCC	2011Q2	126201240	158025090	5605798
1101	TCC	2011Q3	125190869	121472558	4357630
1101	TCC	2011Q4	129320349	129226125	2783801

6. Missing values

missing_summary <- data.frame(
  Variable = names(financial_data),
  Missing_Count = colSums(is.na(financial_data)),
  Missing_Percent = round(colMeans(is.na(financial_data)) * 100, 2)
)
knitr::kable(missing_summary)

	Variable	Missing_Count	Missing_Percent
stock_id	stock_id	0	0.00
company_name	company_name	0	0.00
year_quarter	year_quarter	0	0.00
book_value_total_equity	book_value_total_equity	6	0.00
market_value_common_stock	market_value_common_stock	11791	8.95
operating_profit_quarter	operating_profit_quarter	18366	13.94

Missing observations have been retained as NA; they have not been replaced with zeros.

7. Duplicate company-quarter observations

duplicate_count <- sum(duplicated(financial_data[c("stock_id", "year_quarter")]))
data.frame(Duplicate_Company_Quarter_Records = duplicate_count)

##   Duplicate_Company_Quarter_Records
## 1                                 0

8. Example: TSMC (stock ID 2330)

tsmc_2010 <- subset(
  financial_data,
  stock_id == "2330" & year_quarter %in% c("2010Q1", "2010Q2", "2010Q3", "2010Q4")
)
knitr::kable(tsmc_2010)

	stock_id	company_name	year_quarter	book_value_total_equity	market_value_common_stock	operating_profit_quarter
21640	2330	TSMC	2010Q1	532304702	1593081794	34127662
21641	2330	TSMC	2010Q2	496872737	1569844030	40468693
21642	2330	TSMC	2010Q3	540904077	1606255266	43065502
21643	2330	TSMC	2010Q4	578704405	1839615538	41513478

9. Data limitations and interpretation

This is a processed TEJ export. The supplied source was filtered using four-digit stock IDs, not an independently verified TWSE-listing-status field. Consequently, the coverage of all TWSE-listed firms has not yet been confirmed; some TPEx or other four-digit identifiers may be included.
Quarterly operating profits were calculated from values believed to be year-to-date cumulative operating income. The quarterly calculation should be verified against the TEJ single-quarter series before treating it as confirmed.
Monetary figures retain the exported data’s scale. Verify the currency/unit setting in the original TEJ download before labeling numbers as dollars or thousands of dollars.
The reporting period is 2010 Q1 through 2026 Q2; not every security necessarily has observations for every quarter.

10. Conclusion

The report loads and summarizes the quarterly financial-data file, checks reporting-period coverage and missing values, and checks whether company-quarter records are duplicated. Full compliance with the assignment’s all listed firms requirement remains subject to verification using TEJ exchange-listing information.