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SOI Tax Stats - Private Foundations Study Data Sources and Limitations

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This page contains information about data sources and limitations for SOI's Private Foundations study.

Please visit the Domestic Private Foundations and Nonexempt Charitable Trust Statistics to access the annual data tables, articles, and publicly available microdata from the study.


The private foundations statistics produced by the Statistics of Income (SOI) Division are based on a sample of Forms 990-PF that are filed with the Internal Revenue Service for a particular tax year. The SOI sample of private foundations is stratified based on both the size of fair market value of total assets and the type of organization (either a private foundation or an IRC section 4947(a)(1) nonexempt charitable trust). All returns filed by nonexempt charitable trusts, regardless of asset size, are selected for inclusion in the study. The private foundation sample is designed to provide reliable estimates of total assets and total revenue. To accomplish this, 100 percent of returns filed for foundations with fair market asset value of $10 million or more are included in the samples, since these organizations represent the vast majority of financial activity. The remaining foundation population is randomly selected for the sample at various rates, ranging from 1 percent to 100 percent, depending on asset size. See Figure A (below) for sample and population counts from the annual SOI studies of private foundations.

Efforts are made to verify that organizations selected into the sample are properly classified as foundations or trusts. The relatively few foundations in the sample that are incorrectly selected as trusts are ultimately treated as foundations for the SOI statistics, and the relatively few trusts incorrectly sampled as foundations are also reclassified. However, the weights used for these organizations are based on the original sample selection classification.

For a given tax year, SOI’s population estimates differ from the actual population of Forms 990-PF returns that post to the IRS Business Master File during the two-year sampling period. This results from sample code changes and the effects of returns that are “rejected” from the sample as part of the editing process. For example, foreign returns and duplicate filings by a single organization are included in the IRS counts of the actual population of Forms 990-PF filed, but are rejected from the SOI estimates.

The data presented are obtained from returns as originally filed with IRS. In most cases, changes made to the original return because of administrative processing or audit procedures are not captured in the statistics. Changes made based on taxpayer amendment are captured, if available. The data are subjected to comprehensive testing and correction procedures in order to ensure statistical reliability and validity. A general discussion of the reliability of estimates based on samples, methods for evaluating both the magnitude of sampling and non-sampling error, and the precision of sample estimates can be found in the general Appendix of the most recent SOI Bulletin.

Figure A

Tax Year

Includes Forms 990-PF processed between:

All Forms 990-PF

Private
Foundations

Nonexempt
Charitable Trusts

Sample
count

Population count

Sample
count

Population count

Sample
count

Population count

1985

Jan. 1, 1986 - Dec. 31, 1987

1,930

32,691

1,930

32,691

-

-

1986

Jan. 1, 1987 - Dec. 31, 1988

2,989

36,376

2,989

36,376

-

-

1987

Jan. 1, 1988 - Dec. 31, 1989

4,923

36,600

4,923

36,600

-

-

1988

Jan. 1, 1989 - Dec. 31, 1990

5,229

38,504

5,229

38,504

-

-

1989

Jan. 1, 1990 - Dec. 31, 1991

5,651

42,702

4,280

39,812

1,371

2,890

1990

Jan. 1, 1991 - Dec. 31, 1992

5,956

44,118

4,541

41,231

1,415

2,887

1991

Jan. 1, 1992 - Dec. 31, 1993

5,665

45,414

4,455

42,526

1,210

2,888

1992

Jan. 1, 1993 - Dec. 31, 1994

5,852

46,698

4,662

43,767

1,190

2,931

1993

Jan. 1, 1994 - Dec. 31, 1995

5,419

48,223

4,253

45,570

1,166

2,653

1994

Jan. 1, 1995 - Dec. 31, 1996

5,948

50,487

5,065

47,971

883

2,516

1995

Jan. 1, 1996 - Dec. 31, 1997

6,388

52,070

5,579

49,823

809

2,247

1996

Jan. 1, 1997 - Dec. 31, 1998

7,552

55,315

6,261

52,297

1,291

3,018

1997

Jan. 1, 1998 - Dec. 31, 1999

8,412

60,533

7,208

57,463

1,204

3,070

1998

Jan. 1, 1999 - Dec. 31, 2000

8,758

64,595

7,783

61,425

975

3,170

1999

Jan. 1, 2000 - Dec. 31, 2001

8,045

68,367

7,039

65,254

1,006

3,113

2000

Jan. 1, 2001 - Dec. 31, 2002

8,202

72,605

7,236

69,575

966

3,030

2001

Jan. 1, 2002 - Dec. 31, 2003

6,465

75,643

5,644

72,644

821

2,999

2002

Jan. 1, 2003 - Dec. 31, 2004

6,301

79,333

5,507

76,307

794

3,026

2003

Jan. 1, 2004 - Dec. 31, 2005

10,537

81,962

7,302

78,727

3,235

3,235

2004

Jan. 1, 2005 - Dec. 31, 2006

11,451

84,216

7,805

80,570

3,646

3,646

2005

Jan. 1, 2006 - Dec. 31, 2007

12,003

86,896

8,244

83,137

3,759

3,759

2006

Jan. 1, 2007 - Dec. 31, 2008

12,741

88,886

9,112

85,257

3,629

3,629

2007

Jan. 1, 2008 - Dec. 31, 2009

12,972

91,220

9,407

87,655

3,565

3,565

2008

Jan. 1, 2009 - Dec. 31, 2010

14,693

100,997

8,533

94,837

6,160

6,160

2009

Jan. 1, 2010 - Dec. 31, 2011

16,900

102,811

10,652

96,563

6,248

6,248

2010

Jan. 1, 2011 - Dec. 31, 2012

17,619

103,802

11,003

97,186

6,616

6,616

2011

Jan. 1, 2012 - Dec. 31, 2013

17,624

103,865

11,092

97,333

6,532

6,532

Page Last Reviewed or Updated: 12-Aug-2014