Area-Specific Recreation 

Use Estimation Using 

the National Visitor Use 

Monitoring Program Data

Eric M. White, Stanley J. Zarnoch, and Donald B.K. English1

United States 

Department of 

Agriculture

Forest Service

Pacific Northwest 

Research Station

Research Note

PNW-RN-557

July 2007

1Eric M. White is a research economist, Pacific Northwest Research Station, Forestry Sciences 

Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331; Stanley J. Zarnoch is a mathematical statistician, Southern Research Station, Forest Inventory, Monitoring, and Analysis, 

200 Weaver Blvd., Asheville, NC 28804; and Donald B.K. English is visitor use monitoring 

program manager, 1400 Independence Ave. SW, Washington, DC 20250-1125. 

Abstract

Estimates of national forest recreation use are available at the national, regional, 

and forest levels via the USDA Forest Service National Visitor Use Monitoring 

(NVUM) program. In some resource planning and management applications, 

analysts desire recreation use estimates for subforest areas within an individual 

national forest or for subforest areas that combine portions of several national 

forests. In this research note we have detailed two approaches whereby the NVUM 

sampling data may be used to estimate recreation use for a subforest area within a 

single national forest or for a subforest area combining portions of more than one 

national forest. The approaches differ in their data requirements, complexity, and 

assumptions. In the “new forest” approach, recreation use is estimated by using 

NVUM data obtained only from NVUM interview sites within the area of interest. In the “all-forest information” approach, recreation use is estimated by using 

sample data gathered on all portions of the national forest(s) that contain the area 

of interest. 

Keywords: Recreation visits, National Visitor Use Monitoring program, 

recreation use estimation, recreation area.

Introduction

Recreation use estimates from the National Visitor Use Monitoring (NVUM) 

program, which are developed at the national, regional, and forest levels, are useful 

for many administrative and management analyses. However, for some situations, 

analysts desire recreation use estimates for areas below the level of a national forest 


Research note pnw-rn-557

or for areas that encompass subforest portions of more than one national forest. In 

this research note, we describe two approaches that can be used to develop these 

area-specific NVUM recreation use estimates. 

We intend for the approaches to be applied in estimating recreation use for 

geographically large areas. The approaches are not appropriate for estimating 

recreation use at individual recreation sites, a collection of a few recreation sites, 

or small portions of the undeveloped areas of the national forest. Some appropriate applications include (1) estimating the national forest recreation use for a large 

watershed that is of particular management interest, (2) estimating recreation use 

for a large separate unit of a national forest (e.g., the western unit of the Hiawatha 

National Forest), or (3) developing an estimate of recreation use for a national forest 

that is part of a multiple-forest administrative unit (e.g., an estimate for the Huron 

National Forest portion of the Huron-Manistee National Forest). For example, the 

approaches described in this paper have been considered for use in estimating 

national forest recreation visitation within the Chattooga River Watershed, which 

is located along the borders of South Carolina, Georgia, and North Carolina and 

encompasses portions of three national forests. Before undertaking area-specific 

estimation, we urge analysts to familiarize themselves with the NVUM sampling 

program and to discuss their analysis with NVUM national-level staff.

National Visitor Use Monitoring Program

The foundations of the NVUM program were initiated in 1996 as a pilot project 

(Zarnoch et al. 2002) and officially implemented across the entire National Forest 

System (NFS) starting in calendar year 2000 (English et al. 2002). During NVUM 

round 1 (lasting from January 2000 through September 2003), each national forest 

in the NFS underwent NVUM sampling for 1 year. We include a brief description 

of the NVUM program and sampling approach; while a more detailed description is 

available in English et al. (2002).

Under NVUM, recreation use is quantified in terms of “site visits” and 

“national forest visits.” A site visit is defined as “one person entering and exiting 

a recreation site or area on a national forest for the purpose of recreation” and a 

national forest visit is defined as “one person entering and exiting a national forest 

for the purpose of recreation” (English et al. 2002). In the course of a single national 

forest visit, an individual may complete multiple site visits (e.g., an individual 

recreating at two day-use sites during a single national forest visit or an individual 

recreating in the undeveloped portion of a forest and at a campground during a 

single national forest visit). Based on NVUM round 1, the NFS had 246 million site 

visits and 205 million national forest visits annually (USDA Forest Service 2004).

We intend for the 

approaches to be 

applied in estimating 

recreation use for 

geographically 

large areas. 


Area-Specific Recreation Use Estimation Using the National Visitor Use Monitoring Program Data

NVUM Sampling Approach

The NVUM sampling approach estimates recreation use by combining traffic 

counts with information gathered via surveys of national forest visitors. Traffic 

counts are completed for a 24-hour period and visitor questionnaires are administered at selected interview locations on selected days (termed sample days) within 

individual national forests. Sample days within a given national forest are selected 

via a stratified random sample from the population of all possible interview locations and days (termed site days) identified for that national forest. 

Site days (and their subset sample days) are stratified by the type of recreation 

area (termed the site type) and by the expected level of last-exiting recreation use 

(termed the use level). Four site types are recognized in the NVUM sampling 

protocol: day use developed sites (DUDS), overnight use developed sites (OUDS), 

general forest area (GFA), and designated wilderness (wilderness).2 A detailed 

definition of the four site types can be found in English et al. (2002). In the first 

round of NVUM, each site day was classified into one of four use levels (high, 

medium, low, and closed) based on the expected level of last exiting recreation 

traffic. Beginning in NVUM round 2, a fifth use level, “very high,” was added. The 

levels of last-exiting recreation traffic that distinguish one use level from another 

within specific site types are identified by personnel on the respective national 

forest. The combination of site type and use level (e.g., DUDS-medium) form the 

strata for the nonproxy NVUM sample. 

Visitation to some recreation sites and areas (e.g., campgrounds, wilderness 

areas, etc.) requires users to pay a fee, obtain a permit, or both to recreate at the 

individual site or in the specific area. For some of these sites and areas, the amount 

of “traffic” can be determined via fee or permit data, and an NVUM traffic count 

is not required. Under NVUM, these sites are termed proxy sites. The proxy count 

is combined with data from the visitor questionnaires to estimate the recreation use 

at the proxy sites. Proxy sites are classified based on site type (i.e., DUDS, OUDS, 

GFA, or wilderness) and the type of proxy employed (e.g., a fee envelope, a permit, 

etc.). These sites are not classified by the level of last-exiting recreation use. Under 

the NVUM protocols and in the approaches described in this research note, proxy 

sites are treated separately from nonproxy sites when estimating recreation use. The 

NVUM proxy sites are identified in the prework analysis completed by national 

forest personnel. 

2 An additional site type recognized under NVUM is “viewing corridor.” Use of this 

type of site or area is not treated as national forest recreation use and this site type is not 

considered here.


Research note pnw-rn-557

Estimates of recreation use in the various nonproxy and proxy strata (e.g., 

DUDS-medium, OUDS-fee envelope, etc.) are constructed from the NVUM 

sampling on a given national forest within the respective strata. The NVUM 

recreation use estimate for that national forest is then developed by summing 

the estimates of use (site visits and national forest visits) for all the nonproxy 

and proxy strata of the forest. Regional and national estimates are computed, in 

turn, by aggregating the visitation estimates of forests within a region and all 

forests in the Nation, respectively. 

Estimating Area-Specific Recreation Use

We label the two approaches to estimating area-specific recreation use as the “new 

forest” approach and the “all-forest information” approach. In the former approach, 

recreation use is estimated for the area of interest (AOI) by using NVUM sample 

days and NVUM visitor surveys completed only at NVUM interview locations 

within the AOI. In the latter approach, recreation use for the AOI is estimated based 

on information obtained from sample days and visitor interviews completed on all 

portions of the forest(s) containing the AOI. 

The new forest approach is feasible only with an appropriate number of sample 

days and visitor interviews within each stratum (i.e., DUDS-high, GFA-low, etc.) in 

the AOI. This restriction may preclude the use of this approach in many situations. 

Application of the new forest approach requires access to the prework data, the 

daily summary data, the proxy data, and the last-exiting recreation visitor survey 

data for the forest(s) involved (see “Glossary” for further information on these data). 

The all-forest information approach does not require that a minimum number 

of sample days or last-exiting recreation visitor surveys were completed within 

the AOI because data from all observations on the forest(s) are incorporated 

in estimating AOI recreation use. However, adoption of this approach requires 

the assumption that the patterns of recreation use within the AOI are similar to 

recreation use patterns on the entire national forest(s). To complete the all-forest 

information procedures, an analyst must have access to the prework data, the forest 

strata sampling results, the proxy data, and the last-exiting recreation visitor survey 

data for the forest(s) involved (see “Glossary” for definitions of these data). 

Much of the information required to complete either approach is available in 

the Natural Resource Information System Human Dimensions-NVUM (NRIS 

HD-NVUM) application. The NRIS HD-NVUM application is available for 

download by USDA Forest Service personnel from the NRIS intranet Web site. 

The NRIS HD-NVUM application contains some information from the prework 

data, the daily summary data, the forest strata sampling results, and the proxy 

The new forest 

approach is 

feasible only with 

an appropriate 

number of sample 

days and visitor 

interviews within 

each stratum in the 

area of interest (AOI).
Area-Specific Recreation Use Estimation Using the National Visitor Use Monitoring Program Data

data. Particularly useful tables and records include table 31 “Summary Results 

by Sampling Stratum,” table 32 “Proxy Summary Results,” table 33 “Results 

From Each Completed Nonproxy Survey Day,” and the interview site records. We 

recommend that analysts obtain the most recent version of this application when 

completing area-specific recreation use estimation. 

Initial Steps in Area-Specific Recreation Use Estimation

Three initial steps are required regardless of which estimation approach is adopted: 

(1) identification and mapping of the AOI, (2) identification of AOI NVUM interview locations, and (3) determination of the population of site days within site 

type/use level strata for nonproxy sites and site type/proxy type strata for proxy 

sites within the AOI. Step 1 is completed by using applicable forest maps and/or 

spatial databases, and steps 2 and 3 are completed by using the prework that was 

completed by personnel on the national forest(s) prior to NVUM sampling. 

Identify and map the area of interest—

The AOI should be delineated based on the management activity, planning issue, 

or the research question being addressed. The adopted spatial boundaries should be 

mapped either on paper map(s) or via a geographic information system (GIS). 

Identify AOI NVUM interview locations—

In the NVUM prework, forest personnel have identified locations throughout the 

national forest for visitor interviews and traffic counts. From the NVUM interview 

locations included in the prework, those that can be used to measure recreation use 

within the AOI should be identified. These AOI NVUM interview locations will 

be used both in estimating the population of site days for the AOI and in identifying the NVUM sample days that can be used to estimate area-specific recreation 

use via the new forest approach. In selecting the AOI interview sites, the goal is to 

identify NVUM interview locations that “capture” visitors who have recreated in 

the AOI and do not “capture” (or capture very few) recreation users who have not 

recreated within the AOI (fig. 1). In cases where an interview site captures both a 

large number of AOI and non-AOI visitors, analysts must use judgment in deciding 

whether to include the site as an AOI interview location. 

All DUDS and OUDS interview locations that fall within the boundaries of the 

AOI should be identified as AOI interview locations. All GFA and wilderness interview locations within the AOI should also be included as long as they exclusively 

(or nearly exclusively) measure AOI recreation use. The NVUM interview locations 

located near but outside the AOI boundary should be examined to determine if 

they primarily capture recreation users exiting from the AOI and should thus be 


Research note pnw-rn-557

included as AOI interview locations. For example, a GFA site located outside the 

AOI boundary but on a road used exclusively (or nearly exclusively) by recreation 

users from the AOI should likely be included as an AOI interview location (see GFA 

sites located outside the AOI boundary in fig. 1). Similarly, a wilderness interview 

location outside the AOI that primarily captures recreation users leaving a wilderness area located within the AOI should likely also be included as an AOI interview 

location. 

In standard NVUM forest-level applications, interview sites are identified by 

individual forests to measure recreation use on the forest being sampled. In some 

cases, an interview location established for one forest’s NVUM sampling may also 

Figure 1—Area of interest (AOI) and non-AOI National Visitor Use Monitoring (NVUM) interview locations for an example AOI. 

DUDS = day use developed sites, GFA = general forest area, OUDS = overnight use developed sites, wilderness = designated wilderness.
Area-Specific Recreation Use Estimation Using the National Visitor Use Monitoring Program Data

have been established for NVUM sampling by an adjacent national forest, and both 

forests may measure the same recreation use at this location (regardless of whether 

or not the forests were sampled in the same year). When estimating AOI recreation 

use in multiple forest applications, interview sites that have been established by 

more than one forest and that measure the same recreation use will lead to a double 

counting of recreation visits if no corrective action is taken (see examples in the 

next paragraph). To avoid double counting, these duplicate interview locations must 

be identified and the number of site days adjusted, as described in the next step.3

Several examples may help to clarify what situations may result in duplicate 

interview locations and the double counting of recreation visits. The most clear 

duplicate interview location situation (and likely the rarest) is one in which two or 

more forests have identified the same OUDS or DUDS site as an interview location 

and measure the same recreation use at that site. For example, if a DUDS picnic 

ground was located in the AOI on the border of two forests and both forests identified this as an interview location, these interview locations would clearly represent 

duplicates and should be identified. In some cases, the same DUDS or OUDS AOI 

interview site may have been identified by multiple forests but may in fact measure 

different recreation use and would not represent duplicates. For example, a DUDS 

site identified by two forests may have two trailheads, each serving trails on the 

respective forests. In this case, the interview location does not measure the same 

recreation use (recreation use on the trail on forest B would not be counted in the 

recreation use estimate of forest A) and the established NVUM interview locations 

are not duplicates. Less straightforward is the identification of duplicate GFA and 

wilderness interview locations. The key to correct identification is determining if 

the GFA and wilderness interview locations established by the forests measure the 

same recreation use. For example, two interview locations established at a single 

GFA parking lot located on the border of two forests would represent duplicates if 

the parking lot is used by canoeists and kayakers taking-out after recreating on a 

river that forms the boundary of the forests. Ultimately, many situations will likely 

be unique, and the analyst will have to use judgment in consultation with nationallevel NVUM personnel to determine if duplicate interview locations are present. 

3 In some instances, a particular recreation site may be identified as two NVUM interview 

locations, both having different site types. For example, both an OUDS interview location 

and a DUDS interview location may have been identified within a developed campground 

that also provides day use lake access. Similarly, a DUDS location and a wilderness location may be identified within a single day use site with picnic grounds and a trailhead into a 

wilderness area. These are valid NVUM interview locations and should not be considered 

duplicates.


Research note pnw-rn-557

Determining the population of site days—

Using the calendar that was constructed for each AOI interview location in the 

NVUM prework, determine the number of site days identified within each stratum 

(e.g., DUDS-medium, OUDS-fee envelope, etc.), keeping proxy and nonproxy 

sites separate, for the AOI NVUM interview locations (table 1). Operationally, this 

involves determining the number of site days identified in the NVUM prework for 

each AOI NVUM interview location, then summing across AOI interview locations 

within strata. When more than one national forest is involved, it is advantageous 

to identify the number of site days within strata separately for each forest involved 

(table 2). 

Table 1—Determining the NVUM site day population for an 

example area of interest

Site typea Use level Site days

Nonproxy locations:

DUDS High 175

Medium 334

Low 1,195

Closed 121

OUDS High 1

Medium 37

Low 207

Closed 120

GFA High 1,063

Medium 3,351

Low 6,382

Closed 7,454

Wilderness High 70

Medium 300

Low 888

Closed 1,297

Proxy locations:

DUDS Fee envelope (open) 71

Fee envelope (closed) 294

OUDS Fee envelope (open) 143

Fee envelope (closed) 587

GFA Fee envelope (open) 275

Fee envelope (closed) 90

 Total 24,455

 Total (excluding closed site days) 14,492

a

DUDS = day use developed sites, OUDS = overnight use developed sites, GFA = 

general forest area, and wilderness = designated wilderness.

When more than 

one national forest 

is involved, it is 

advantageous to 

identify the number of 

site days within strata 

separately for each 

forest involved.


Area-Specific Recreation Use Estimation Using the National Visitor Use Monitoring Program Data

Table 2—Determining the NVUM site day population for an example area of interest 

involving multiple forests

Site typea Use level Forest A Forest B Forest C All three

Nonproxy locations:

DUDS High 22 0 153 175

Medium 177 35 122 334

Low 45 1,060 90 1,195

Closed 121 0 0 121

OUDS High 0 1 0 1

Medium 0 37 0 37

Low 0 207 0 207

Closed 0 120 0 120

GFA High 895 168 0 1,063

Medium 1,123 883 1,345 3,351

Low 599 3,718 2,065 6,382

Closed 3,588 3,261 605 7,454

Wilderness High 0 70 0 70

Medium 37 263 0 300

Low 77 597 214 888

Closed 251 895 151 1,297

Proxy locations:

DUDS Fee envelope (open) 71 0 0 71

Fee envelope (closed) 294 0 0 294

OUDS Fee envelope (open) 143 0 0 143

Fee envelope (closed) 587 0 0 587

GFA Fee envelope (open) 275 0 0 275

Fee envelope (closed) 90 0 0 90

 Totals 8,395 11,315 4,745 24,455

 Totals (excluding closed site days) 3,464 7,039 3,989 14,492

a

DUDS = day use developed sites, OUDS = overnight use developed sites, GFA = general forest area, and 

wilderness = designated wilderness.

When duplicate NVUM interview locations have been identified for the same 

physical location, site days at the duplicates that correspond to measurement of the 

same recreation use should be counted only once. Generally, analysts will simply 

include the site days at the interview location established by one of the forests and 

discard the site days established by the other forests. In some cases, the open season 

(the nonclosed site days) established by one forest may be longer than that established by the other forests. In these cases, it is likely best to use the longer open 

season site days and exclude the site days established by the other forests to ensure 

that recreation use is estimated based on the longest season. 
10

Research note pnw-rn-557

In rare cases, the established site days on forest A and forest B may measure 

duplicate recreation use for part of the year and unique recreation use during 

another part of the year (e.g., an interview location at a trailhead for a single trail 

that is open on forest A all year but closes on forest B during part of the year owing 

to snow conditions). In these cases, the site days that measure duplicate recreation 

use should be counted only once. The site days that measure unique recreation use 

at this duplicate location should then be added to the duplicate site day total. Again, 

many duplicate interview location situations will be unique, and the analyst should 

use judgment and consult national-level NVUM personnel. 

Estimating Area-Specific Recreation Use 

Via the New Forest Approach

Determining the Adequacy of the NVUM Sample

Under the new forest approach, NVUM sample days and visitor interviews within 

the AOI are used to develop estimates of the number of site visits within the AOI 

and the number of AOI visits (AOI visits are analogous to national forest visits). To 

develop reliable estimates of AOI recreation use, there must be both a reasonable 

number of sample days and a reasonable number of visitor interviews within each 

stratum in the AOI. 

Based on the NVUM sampling protocol, we recommend a minimum of 8 

sample days for each nonproxy stratum and a minimum of 4 sample days for each 

proxy stratum (English et al. 2002). When the population of site days in a stratum 

is less than 8 or otherwise small, it is more important to ensure that the number of 

sample days is reasonable and the sampling fraction (site days to sample days) is 

adequate rather than being constrained solely by the 8-sample-day minimum. For 

example, if there are only 7 site days in a given stratum, then 4 sample days may be 

appropriate. Similarly, if just 16 site days exist within a stratum, then 7 sample days 

may be reasonable. 

Having a reasonable number of visitor interviews within each stratum is likely 

more restrictive than meeting the NVUM minimum number of sample days. At 

nonproxy sites, data gathered via visitor interviews are used to estimate (1) the percentage of visitors who are last-exiting recreationists, (2) the average party size of 

last-exiting recreation parties, and (3) the number of sites visited per national forest 

visit. At proxy sites, data from last-exiting recreation visitors are used to “calibrate” 

the proxy in order to estimate recreation use. Because the NVUM protocols do not 

identify the minimum number of recreation visitor interviews within each stratum, 

analysts must determine what is reasonable for their specific application. 
11

Area-Specific Recreation Use Estimation Using the National Visitor Use Monitoring Program Data

Having a less than adequate number of sample days and/or a limited number 

of visitor interviews in one or more nonproxy strata does not immediately preclude 

using the new forest approach. However, if several nonproxy strata have a small 

number of sample days, or a very limited number of visitor interviews, the new 

forest approach is likely not appropriate or may need to be modified (see the later 

section entitled “Options for Meeting Minimum Sample Size Requirements”). 

Individual analysts will have to use judgment as to whether the number of sample 

days and visitor interviews are reasonable given the specific situation. 

Although it is preferable to have at least 4 sample days and a reasonable number 

of visitor interviews in every proxy stratum, it is not entirely necessary (and probably not likely). At proxy sites, the proxy provides a known count of the “traffic” at 

the site and only a conversion factor (obtained from surveys of last-exiting recreation visitors) is needed to convert this proxy count to an estimate of recreation use. 

If necessary, the proxy count can be converted to a recreation use estimate based on 

data from visitor interviews completed at interview locations within the same proxy 

stratum but outside the AOI. The proxy counts themselves are still obtained for 

the individual proxy sites within the AOI. Analyst judgment and local knowledge 

are necessary to determine whether the proxy conversion factor obtained from the 

larger geographic area is appropriate to the proxy sites in the AOI.

General Discussion of Recreation Visit Calculations

The formulas in the following sections are adapted from English et al. 2002. In the 

new forest approach, only data gathered from sample day observations at the AOI 

interview locations are used in estimating recreation use. The use of AOI-specific 

data is designated in the formulas below by the symbol “*”. Estimation of visits 

(both site visits and visits to the AOI in general) is achieved through (1) developing 

estimates of visits in the nonproxy strata, (2) developing estimates of visits in the 

proxy strata, and (3) combining nonproxy and proxy visit estimates into a single 

total visit estimate. Calculations for site visit estimation are detailed first, followed 

by the calculations for AOI visit estimation. 

Calculating Site Visits Within the AOI for Nonproxy Strata

The first step in estimating the number of site visits in the nonproxy strata is to 

estimate the mean number of site visits for given nonproxy stratum h within the 

AOI ( *

SVh ):,

If necessary, the proxy 

count can be converted 

to a recreation use 

estimate based on data 

from visitor interviews 

completed at interview 

locations within the 

same proxy stratum 

but outside the AOI.
12

Research note pnw-rn-557

* * * *

SVh = Ch Ph Vh ,

where *

Ch is the mean number of cars counted on the NVUM traffic counter 

adjusted for the number of axles and two-way traffic in stratum h as estimated 

from the daily summary data, *

Ph is the proportion of exiting traffic that is 

last-exiting recreationists averaged across all sample days in stratum h (also 

estimated from the daily summary data), *

Vh is the number of persons in lastexiting recreation parties averaged across all sample days in stratum h within 

the AOI as estimated from the last-exiting recreation visitor survey data, and * 

designates that this information is drawn from the AOI interview locations. The 

total number of site visits in nonproxy stratum h is computed as

* * * SVh = Nh SVh , [1]

where * Nh is the known population of site days in stratum h within the AOI.

An estimate of the total number of site visits to nonproxy sites within the 

AOI is calculated as

∑=

=

H

h

TOTALSVNP Nh Ch Ph Vh

1

* * * * * ,

where H is the total number of nonproxy strata within the AOI. The total 

site visit equation comes from a summation over the strata of equation 1. 

Assuming independence of *

Ch , *

Ph , and *

Vh , the variance of the total 

nonproxy estimate is

 where ( )

*

V Ch , ( )

*

V Ph , and ( )

*

V Vh are variances calculated in the usual manner. 

Calculating Site Visits Within the AOI for Proxy Strata

Site visit estimates for the proxy strata within the AOI are developed from the 

following: (1) the annual total proxy count for a given site k within a given proxy 

stratum h (APhk ) as identified in the proxy data, (2) the percentage of visitors 

complying with the proxy requirement (e.g., percentage obtaining a wilderness 

permit, etc.) for a given site k within a given proxy stratum h (CRhk) as reported 

in the proxy data, and (3) a conversion factor estimated by using the last-exiting 

recreationists visitor survey data ( *

Ah ). 

∑ ( ) ( ) ( ) ( ) ( ) ( ) =





 



 = + + H

h

TOTAL NP Nh Ph Vh V Ch ChVh V Ph Ch Ph V Vh V SV 1

* 2 * * * 2 * * * 2 2 * * * * ( ) ∑ ( ) ( ) ( ) ( ) ( ) ( ) ,

=





 



 = + + H

h

TOTAL NP Nh Ph Vh V Ch ChVh V Ph Ch Ph V Vh V SV 1

* 2 * * * 2 * * * 2 2 * * * * ( ) ,
13

Area-Specific Recreation Use Estimation Using the National Visitor Use Monitoring Program Data

The first two components (APhk and CRhk ) are combined to develop 

the “compliance-based proxy count” for each proxy site (PChk ): 

hk

hk

hk CR

AP PC = .

In many instances, PChk will be directly available as part of the proxy data 

contained within the NRIS HD-NVUM application. 

Using PChk, the average daily proxy count ( *

PCh ) for a given proxy stratum 

h is calculated as follows:

,

 [2]

where Nhk is the known number of proxy site days for site k in stratum h, and Kh

is the total number of proxy sites in stratum h within the AOI. *

PCh is a known 

constant and, thus, has no variance. This fact is used advantageously later in the 

variance equation for the total proxy estimate. 

The conversion factor *

Ah is constructed incorporating the sum of group size 

for all groups surveyed in stratum h of the AOI on given sample day i ( * SGhi ) and 

the sum of the number of proxies completed by all groups surveyed in stratum h of 

the AOI on sample day i ( * SRhi) (both estimated from the last-exiting visitor survey 

data by using responses to the proxy-specific questions) via the following formula:

∑

∑

=

= = h

h

n

i

hi

n

i

hi

h

SR

SG

A

1

*

1

*

* ,

where nh is the number of sample days in stratum h within the AOI. 

The average number of site visits across all sample days in proxy stratum 

h ( *

SVh ) is then calculated as 

* * *

SVh = Ah PCh . [3]

The total number of site visits in proxy stratum h can be computed by 

expanding in a similar manner as was done in equation 1. 

∑

∑

=

= = h

h

K

k

hk

K

k

hk

h

N

PC

PC

1

1 *

∑

∑

=

= = h

h

K

k

hk

K

k

hk

h

N

PC

PC

1

1 *
14

Research note pnw-rn-557

An estimator for the total number of site visits to all proxy sites within the 

AOI is

* *

1

* *

h h

H

h

TOTALSVp ∑Nh A PC == ,

where all variables are as defined previously. The variance of this estimator is then

∑=

=

H

h

V TOTALSVP Nh PCh V Ah

1

2 * 2 * * * ( ) ( ) ,

where the variance of *

Ah is based on the ratio of means and is computed as

Calculating the Total Number of Site Visits Within the AOI

The total number of site visits within the AOI, combining proxy and nonproxy 

sites, is

* * * TOTALSV = TOTALSVNP + TOTALSVP ,

with variance calculated as

( ) ( ) ( ) * * * V TOTALSV = V TOTALSVNP + V TOTALSVP .

Area of Interest Visits

In most applications, the AOI will likely contain a number of recreation sites and 

areas (i.e., DUDS, OUDS, GFA, and wilderness). Because typically some visitors 

will recreate at multiple locations within the AOI, the number of site visits in the 

AOI will generally be greater than the number of AOI visits. The AOI visits are 

calculated by using, in part, the number of sites visited and whether or not recreation occurred in the GFA or in wilderness areas as reported by individual NVUM 

survey respondents in the last-exiting recreationist survey data. Respondents to 

the NVUM visitor survey identified the number of sites visited, the number of 

days spent in the GFA, and the number of days spent in wilderness areas on their 

current trip to the entire national forest. In some cases, the sites visited, the GFA 

recreation, or wilderness recreation that were reported by individual respondents 

may have occurred outside the AOI. Lacking other information, it is assumed that 

( )





 





+ −















 −

= ∑ ∑ ∑

∑ = = =

=

h h h

h

hi

n

i

n

i

hi hi h hi h

n

i

hi n

i h

h h

h SG A SR A SG SR

n

SR

n n

V A

1 1

* * 2 * * 2 *

1

2 *

2

1

*

*

2

( 1)

1 ( ) . ( )





 





+ −















 −

= ∑ ∑ ∑

∑ = = =

=

h h h

h

hi

n

i

n

i

hi hi h hi h

n

i

hi n

i h

h h

h SG A SR A SG SR

n

SR

n n

V A

1 1

* * 2 * * 2 *

1

2 *

2

1

*

*

2

( 1)

1 ( ) .

Because some visitors 

will recreate at multiple 

locations within the 

AOI, the number of site 

visits in the AOI will 

generally be greater 

than the number of 

AOI visits.
15

Area-Specific Recreation Use Estimation Using the National Visitor Use Monitoring Program Data

the reported site visits and GFA and wilderness recreation all occurred within the 

AOI. If violated, this assumption could yield an underestimation of AOI visits. The 

number of AOI visits would be underestimated because the number of sites visited 

is used to adjust the site visit estimate downward. In rare instances, when the AOI 

contains only GFA or only wilderness areas, the number of AOI visits will equal the 

number of site visits. 

Calculating AOI Visits for Nonproxy Strata

The first step in estimating AOI visits for nonproxy strata is to estimate the number 

of AOI visits on sample day i in stratum h ( * AO hi IV ). This is computed as follows:

* * * * AO hi Chi Ph CBARhi IV = ,

where * Chi the number of cars obtained on the NVUM traffic counter adjusted 

for the number of axles and two-way traffic on sample day i in stratum h within 

the AOI as reported in the daily summary data and *

Ph is as defined previously. 

* CBARhi is computed as

∑=

=

nhi

j hij

hij

hi

hi NS

V

n

CBAR

1 *

*

*

* 1 ,

where * nhi is the number of last exiting vehicles in stratum h on sample day i, * Vhij

is the number of visitors in vehicle j in stratum h on sample day i, and * NShij is the

number of sites visited by individuals in vehicle j in stratum h on sample day i, all 

within the AOI. 

Recreation that was reported to have occurred in the GFA or in wilderness 

areas during the visit (i.e., days in the GFA > 0, days in wilderness > 0) is counted 

as one site visit for that site type regardless of the number of days in the GFA or 

days in wilderness. For example, if a respondent reported visiting 2 DUDS, spending 2 days in the GFA, and spending 3 days in a wilderness area during the national 

forest visit, NShij equals 4 (2 for DUDS visited + 1 for GFA recreation + 1 for 

wilderness recreation). 

The average number of AOI visits across all sample days within nonproxy 

stratum h is computed as 

∑=

=

nh

i h

hi

h

n

AOIV AOIV

1

* *

 .
16

Research note pnw-rn-557

The number of AOI visits in nonproxy stratum h is then computed as

* * *

h h AO h AOIV = N IV , [4]

where * Nh is the known number of site days in stratum h of the AOI. 

An estimate of the total number of AOI visits associated with the nonproxy 

sites in the AOI is calculated as

∑=

=

Nh

h

NP h AO h TOTALAOI N IV

1

* * *

,

with variance 

∑=

=

Nh

h

NP h AO h V TOTALAOI N V IV

1

2 * * * ( ) ( ) ,

where ( )

*

AO h V IV is calculated in the usual manner. 

Calculating AOI Visits for Proxy Strata

The AOI visits for proxy strata are estimated following the same general approach 

as used in estimating site visits for the proxy strata. However, an adjustment factor 

( *

AFh ) is used to account for the number of sites visited per AOI visit. The conversion factor *

AFh is developed as

∑

∑

=

= = h

h

n

i

hi

n

i

hi

h

SR

SC

AF

1

*

1

*

*

,

where * SRhi is as defined previously and * SChi is computed as

( )

1

*

*

*

∑=

= hi J

j hij

hij

hi NS

V

SC ,

where * Vhij is the number of visitors in stratum h on sample day i in party j, * NShij

is the number of sites visited by party j in stratum h on sample day i, and Jhi is the

total number of parties in stratum h on sample day i, all within the AOI. Reported 

recreation in the GFA or wilderness area during the visit (i.e., days in the GFA > 0, 

days in the wilderness > 0) is counted as one site visit for that site type regardless 

of the number of days in the GFA or wilderness area. The average number of AOI 

visits in proxy stratum h ( *

AOIVh ) is computed as

* * *

AOIV h = AFh PCh ,
17

Area-Specific Recreation Use Estimation Using the National Visitor Use Monitoring Program Data

where *

AFh is as computed above and *

PCh is the mean daily proxy count for 

proxy stratum h as calculated by using equation 2. The number of AOI visits in 

proxy stratum h within the AOI ( *

AOIVh ) is then computed by expansion as in 

equation 4. 

An estimate of the total number of AOI visits associated with the proxy sites in 

the AOI is

∑=

=

H

h

P Nh AFh PCh TOTALAOI

1

* * * * ,

with variance

∑=

=

H

h

TOTALAO P Nh PCh V AFh V I

1

2 * 2 * * * ( ) ( ) .

where ( )

*

V AFh is calculated based on the ratio of means in a similar way as ( )

*

V Ah

was as detailed in the previous section.

Calculating the Total Number of AOI Visits

The total number of AOI visits is then

* * *

NP TOTALAO P TOTALAOI = TOTALAOI + I ,

with variance

( ) ( ) ( ) * * *

NP TOTALAO P V TOTALAOI = V TOTALAOI +V I .

Options for Meeting Minimum Sample Size Requirements

Several options are available to meet the minimum sample size necessary to 

complete the new forest estimation approach. In some cases, it may be possible 

to combine adjacent use levels within a given site type (e.g., DUDS-medium and 

DUDS-low), allowing for pooling of sample day observations and last-exiting recreation visitor interviews within the pooled stratum. This option may be particularly 

appropriate if two adjacent use levels (e.g., low and medium) within a single site 

type have small numbers of site days, sample days, or visitor interviews or if one 

use level within a site type has few site days, sample days, or visitor interviews and 

another has many site days, sample days, or visitor interviews. When pooling across 

use levels, the analyst should be cognizant of the potential for introducing bias into 

the visit estimates and for increasing the variance of the resulting recreation use 

estimate. A biased visit estimator may result if the numbers of sample days occurring within the pooled use levels are not proportional to the population of site days 

within the use levels. For example, a biased estimator could result in cases where 

Several options are 

available to meet 

the minimum sample 

size necessary to 

complete the new 

forest estimation 

approach.
18

Research note pnw-rn-557

a similar number of site days exist in two use levels but vastly dissimilar number 

of sample days occurred in the two use levels. Additionally, if the visit behavior of 

recreationists (e.g., party size, number of sites visited, etc.) in the two use levels is 

different, then the resulting estimate could be biased. 

As the second NVUM round is completed, there may be opportunities to 

increase the number of sample days and/or the number of last-exiting visitor interviews within AOI strata by pooling data across NVUM rounds. Significant changes 

within the use level breakpoints or the classification of NVUM interview locations 

within the involved forest(s) may preclude this pooling. Pooling across NVUM 

rounds is not appropriate if there have been significant changes in the amount of 

recreation use on the forest between NVUM rounds. Cross-round pooling will also 

make it impossible to identify trends in recreation use levels between the sample 

years. Analysts should consult national-level NVUM personnel to determine the 

feasibility of pooling across sampling rounds. 

Sample day observations and visitor interviews completed at NVUM interview 

locations near the boundary of the AOI could be combined with sample day observations and visitor interviews within the AOI (within strata). Site days from these 

nearby interview locations should not be included in the total number of site days 

for the AOI (i.e., * Nh ). Incorporation of sample day data and interviews completed 

at nearby interview locations should occur only if recreation use levels (within 

strata) at the nearby interview locations are similar to recreation use levels within 

the AOI. 

In some cases, the new forest approach may become feasible only if information from all portions of the forest can be used in estimating recreation use for 

specific strata (as done in the all-forest information approach presented next). Information from outside the AOI could include the average site visit (SVh ) or average 

national forest visit (NFVh ) estimates for a specific stratum as determined for the 

entire forest, the average number of sites visited per national forest visit in stratum 

h ( NSh ), or the average number of people per vehicle in stratum h (Vh ). As more 

information from outside the AOI is used, the recreation use estimate becomes 

more dependent on the assumption that recreation use patterns within the AOI do 

not differ significantly from recreation use patterns outside the AOI, within strata. 

Estimating Area-Specific Recreation Use Via the 

All-Forest Information Approach

The all-forest information approach involves less complex calculations and does not 

require the analyst to have access to the daily summary data. Analysts must still 

have access to the prework data, the forest strata sampling results, the proxy count 
19

Area-Specific Recreation Use Estimation Using the National Visitor Use Monitoring Program Data

reports, and last-exiting recreationist survey data for all of the national forests 

involved. 

The all-forest information approach assumes that recreation use patterns within 

the AOI do not differ, within strata, from recreation use patterns on the forest(s) 

in general. This approach is likely inappropriate when (1) the level of recreation 

use, within strata, in the AOI is known to differ substantially from the level of use 

on the forest in general within the same strata; or (2) the pattern of site visits per 

national forest visit differs markedly between the AOI and the forest in general. 

The former restriction is not meant to preclude use of this approach in an AOI that 

has lower total levels of recreation use as result of a longer closed season or more 

low-use site days, as this difference is accounted for in the use level stratification of 

site days. 

Calculating Site Visits Within the AOI for Nonproxy Strata

In the all-forest information approach, the average site visits per sample day for 

stratum h (SVh ) is gathered from the forest strata sampling results reported for the 

entire national forest (table 3).4 In multiple-forest applications, the appropriate SVh

are gathered separately for each forest involved (table 4). 

4 For comparison, in the “new forest” approach *

SVh was calculated by using data gathered 

only from within the AOI.

Table 3—Example average number 

of site visits within nonproxy strata 

applied to the area of interest

Average number

Site typea Use level of site visits

DUDS High 236.1

Medium 85.8

Low 47.6

OUDS High 41.3

Medium 32.7

Low 10.7

GFA High 187.7

Medium 54.9

Low 11.1

Wilderness High 85.3

Medium 31.6

Low 13.6

a

DUDS = day use developed sites, OUDS = overnight 

use developed sites, GFA = general forest area, and 

wilderness = designated wilderness.

Table 4—Example average number of site 

visits within nonproxy strata for a multipleforest area of interest

Site typea Use level Forest A Forest B

DUDS High b 53.7

Medium 187.1 42.5

Low 35.5 11.5

OUDS High 41.3 b

Medium 32.7 b

Low 10.7 b

GFA High 61.2 b

Medium 46.5 45.5

Low 5.5 24.2

Wilderness High 85.3 b

Medium 67.3 b

Low 30 13.6

a

DUDS = day use developed sites, OUDS = overnight use 

developed sites, GFA = general forest area, and wilderness = 

designated wilderness.

b

No site days exist within the area of interest on this national 

forest.
20

Research note pnw-rn-557

In single forest applications, equation 1 is used to compute the total number 

of site visits in nonproxy stratum h ( *

SVh ) of the AOI. This calculation uses the 

average site visit estimate for stratum h (SVh) (as estimated for the whole forest) 

and the known number of site days in stratum h occurring in the AOI ( * Nh ). 

An estimate of the total number of site visits for all nonproxy sites can be 

computed as

∑=

=

H

h

TOTALSVNP Nh SVh

1

* *

,

with variance

∑=

=

H

h

V TOTALSVNP Nh V SVh

1

2 * * ( ) ( ) ,

where V (SVh ) is obtained from the forest strata sampling results and H is the

total number of nonproxy strata in the AOI. 

In multiple-forest applications, the total number of site visits for nonproxy AOI 

stratum h ( *

SVh ) is calculated as

hf

F

f

h hf SV ∑N SV =

= 1

* * , [5]

where * Nhf is the number of site days in stratum h of forest f, SVhf is the average 

site visit estimate per sample day in stratum h estimated for all of forest f, and F is

the total number of forests in the AOI. The total number of site visits for nonproxy 

sites (in the multiple-forest application) is computed as

hf

H

h

F

f

TOTALSVNP ∑∑Nhf SV = == 1 1

* *

,

with variance

∑∑= =

=

H

h

hf

F

f

NP hf V TOTALSV N V SV

1 1

2 * * ( ) ( ) ,

where H is the total number of strata within the AOI, ( ) V SVhf is obtained from 

the forest strata sampling results for forest f, and all other variables are as defined 

previously. 

Calculating Site Visits Within the AOI for Proxy Strata

Site visit estimates for proxy sites within the AOI are estimated by using (1) the 

“compliance-based proxy count” for each proxy site k in stratum h (PChk ), (2) the 

number of site days for proxy site k in stratum h (Nhk), and (3) the conversion factor 
21

Area-Specific Recreation Use Estimation Using the National Visitor Use Monitoring Program Data

for proxy stratum h (Ah ) as estimated from proxy sites in stratum h both within and 

outside the AOI and reported in the proxy data. PChk and Ah are available as part of 

the proxy data contained within the NRIS HD-NVUM application. Items 1 and 2 

are used to calculate the average daily proxy count ( *

PCh ) for a given proxy stratum 

h by using equation 2.

Using the average daily proxy count *

PCh and the proxy conversion factor

Ah, the average site visit estimate for proxy stratum h ( *

SVh ) can then be computed 

by employing equation 3. As with nonproxy sites, in single-forest applications, the 

total number of site visits for proxy stratum h ( *

SVh ) is computed by multiplying 

the average site visits for proxy stratum h (SVh) by the number of site days in proxy 

stratum h within the AOI ( * Nh ) (equation 1). 

An estimator for the total number of site visits at proxy sites in the AOI is

∑=

=

H

h

TOTAL P Nh Ah PCh SV

1

* * * .

The variance is

∑=

=

H

h

h h V TOTALSVP Nh PC V A

1

2 2 * * * ( ) ( ) ,

where V (Ah ) is based on the ratio of means as described previously.

In multiple-forest applications, the total number of site visits for proxy strata 

h in the AOI ( *

SVh ) is calculated by using equation 5 and the SVhf values for the 

respective forests.5 An estimate of the total number of site visits for the proxy sites 

in the multiple-forest AOI is then calculated as

∑∑= =

=

H

h

F

f

TOTAL P Nhf Ahf PChf SV

1 1

* * * ,

where * Nhf , Ahf , and *

PChf are as defined previously and determined for the 

respective forest f. The variance of the total site visit for proxy sites is then 

calculated as 

∑∑= =

=

H

h

F

f

TOTAL P Nhf PChf V Ahf V SV

1 1

2 * 2 * * ( ) ( ) ,

where all variable are as defined previously. 

5 If proxy strata occur on only one forest in a multiple-forest application, the “single-forest 

application” calculations can be followed rather than the multiple-forest calculations. 
22

Research note pnw-rn-557

Calculating the Total Number of Site Visits Within the AOI

The total number of site visits within the AOI is

* * * TOTALSV = TOTALSVNP + TOTALSVP ,

with variance calculated as

( ) ( ) ( ) * * * V TOTALSV = V TOTALSVNP +V TOTALSVP . 

Calculating AOI Visits for Both Nonproxy and Proxy Strata

The AOI visits for proxy and nonproxy strata are calculated by using the same 

formulas and are presented together. We present formulas for the multiple-forest 

application, as the single-forest application is simply a special case. 

First, the average number of national forest visits within each nonproxy and 

proxy stratum h (NFVhf ) is computed separately for each forest f as

hf

hf hf

NS

NFV SV 1 = × ,

where SVhf is the average number of site visits in stratum h within forest f.

NShf is the average number of sites visited per national forest visit in stratum h

within forest f and is computed as the arithmetic mean

hf

J

j

hjf

hf

J

NS

NS

∑= = 1 ,

where NShjf is the number of sites visited as reported by individual j in stratum h

within forest f. Reported recreation in the GFA or wilderness during the visit (i.e., 

days in the GFA > 0, days in wilderness > 0) is counted as one site visit for that site 

type regardless of the number of days in the GFA or wilderness. Jhf is the number of 

individuals sampled within stratum h of forest f. The total number of AOI visits for 

nonproxy strata h ( * NFVh ) is computed as

hf

F

f

NFVh ∑Nhf NFV == 1

* * ,

where * Nhf is the number of site days in stratum h of forest f within the AOI and 

F is the total number of forests within the AOI. 
23

Area-Specific Recreation Use Estimation Using the National Visitor Use Monitoring Program Data

An estimate of the total number of AOI visits calculated for either proxy 

( * TOTALAO P I ) or nonproxy strata ( * TOTALAO NP I ) is

∑∑= =

=

H

h

hf

F

f

TOTALAOI Nhf NFV

1 1

* *

with variance

∑ ∑= =

=

H

h

hf

F

f

V TOTALAOI Nhf V NFV

1 1

2 * * ( ) ( ) ,

where V (NFVhf ) is the variance of NFVhf and is calculated in the usual manner 

and all variables are as defined previously.

Calculating the Total Number of Visits to the AOI

An estimate of the total number of AOI visits for proxy and nonproxy strata 

combined is

* * *

NP TOTALAO P TOTALAOI = TOTALAOI + I

with variance

( ) ( ) ( ) * * *

NP TOTALAO P V TOTALAOI = V TOTALAOI +V I .

Multiple Forest AOI Visit Adjustment

The NVUM visitor survey respondents complete the questionnaire in regard to 

the current visit they are completing to the national forest on which they were 

sampled. When completing the questionnaire, respondents report the number of 

sites visited and recreation in the GFA and wilderness that occurred during the 

current national forest visit. This information is used to determine the number of 

site visits occurring per national forest visit. Respondents do not report visits to 

sites, GFA recreation use, or wilderness recreation use on adjacent national forests 

that may have occurred during the respondent’s current recreation trip. Because 

the borders within the AOI between the multiple forests now represent internal 

divisions that are being assumed away, visits to the AOI that include unreported 

site visits, GFA recreation use, or wilderness recreation use on land within the AOI 

managed by another forest during the same trip will yield an inflated AOI visit 

estimate. To correct for this, the final AOI visit estimate should be divided by the 

mean number of forests visited during an AOI visit (this mean should be greater 

than or equal to 1.0). These data are not available in the NVUM data, and thus local 

information and analyst judgment must be used to determine the appropriate value 

When completing 

the questionnaire, 

respondents report 

the number of 

sites visited and 

recreation in the 

GFA and wilderness 

that occurred during 

the current national 

forest visit.
24

Research note pnw-rn-557

for the adjustment. Note that the potential overestimation of AOI visits owing to 

unreported site visits and GFA recreation on other AOI forests may be offset by 

a potential underestimation of AOI visits resulting from the assumption that all 

reported site visits and GFA recreation use occurred within the AOI (when it may 

have in fact occurred outside the AOI). In some cases, it may be best to assume 

that these balance 

and no multiple-forest AOI visit adjustment be taken. 

If a site day adjustment for duplicate interview locations has already been 

taken, a multiple-forest AOI visit adjustment does not need to be adopted for that 

portion of recreation use associated with the duplicate interview locations, as it 

has already been accounted for by ensuring that the site days are counted only 

once. The remaining recreation use not associated with the duplicate interview 

locations is still subject to the multiple-forest AOI visit adjustment. 

Summary 

Currently, NVUM-based recreation visitation estimates are reported at the 

national, regional, and forest levels. In this research note, we have described two 

approaches for estimating recreation use within large subforest areas by using 

NVUM data. These subforest areas may fall within a single forest or within 

multiple forests. The two approaches differ in data requirements, complexity of 

estimation, and assumptions required. The new forest approach requires access 

to more of the NVUM data and is more analytically complex than the all-forest 

information approach. Although the all-forest information approach requires less 

data and is less complex, it requires the assumption that recreation-use patterns 

within the area of interest are similar to those found on the forest in general, 

within strata. Regardless of the approach adopted, analysts are strongly encouraged to coordinate their area-specific recreation use estimation with nationallevel NVUM personnel.
25

Area-Specific Recreation Use Estimation Using the National Visitor Use Monitoring Program Data

Glossary

daily summary data—These data, available in the Natural Resources Information 

System Human Dimensions-National Visitor Use Monitoring (NRIS HD-NVUM) 

application and from NVUM national-level personnel, identify the calculated traffic 

count, number of visitor contacts, and number of last-exiting visitor interviews for 

each sample day. 

forest strata sampling results—Data available in the NRIS HD-NVUM 

application and from national-level NVUM personnel that identify the average 

number of site visits, number of visitor contacts, and the number of last-exiting 

visitor interviews, by strata.

interview location—A location where NVUM sampling could occur, identified 

and classified into one of the four site types by local forest personnel.

last-exiting recreation traffic—Vehicles or visitors leaving the site or general 

forest area for the last time during the current visit. 

last-exiting visitor survey data—Data from NVUM questionnaires completed 

by individuals contacted during sample days at NVUM interview locations who 

were recreating on the national forest and who were exiting the site or general 

forest area for the last time that day.

national forest visit—One person entering and exiting a national forest for the 

purpose of recreation (English et al. 2002).

prework data—Information developed by forest personnel in preparation for 

NVUM sampling and available to a limited extent in the NRIS HD-NVUM 

application. These data include the identification of NVUM interview locations 

and the classification of those locations by site type and use levels for every day 

of the year. This classification yields the sampling frame, which is used to develop 

the sample calendar. Analysts are urged to contact forest-level personnel who 

completed the prework. 

proxy data—Available in the NRIS HD-NVUM application and from NVUM 

national-level personnel, these data include the forest-reported proxy count, the 

number of site days at the proxy site, the compliance-adjusted proxy count, and 

the conversion factor to adjust the proxy count to number of site visits. 

proxy sites—Recreation sites or areas where some other information (e.g., permits, 

fee envelopes, ski lift tickets, etc.) exists that can be used to quantify the amount of 

recreation visitation. The type of “other information” (i.e., fee envelopes, permits, 

etc.) determines the “proxy type” of the interview site. 
26

Research note pnw-rn-557

sample day—An interview location and date selected by stratified random sample 

when NVUM sampling occurs. 

site days—The population of all possible interview locations and days on a national 

forest. 

site type—One of four types of recreation sites as defined for NVUM sampling: 

day use developed sites (DUDS), overnight use developed sites (OUDS), general 

forest area (GFA), designated wilderness (wilderness). 

site visit—One person entering and exiting a recreation site or area on a national 

forest for the purpose of recreation (English et al. 2002).

strata—The combination of site type and use level (e.g., DUDS-high, OUDS-low, 

etc.) for nonproxy sites or the combination of site type and proxy type (e.g., 

OUDS-fee envelope, DUDS-ticket) for proxy sites. 

use level—The expected level of last-exiting recreation traffic at a given interview 

location on a given day as identified by local forest personnel in the prework. Four 

use levels were recognized in NVUM round 1: high, medium, low, and closed. In 

NVUM round 2, a fifth use level, very high, was also included. 

Acknowledgments

We thank Susan Alexander, J. Ross Arnold, and Daniel McCollum for their helpful 

comments on an earlier version of this research note. 

References

English, D.B.K.; Kocis, S.M.; Zarnoch, S.J.; Arnold, J.R. 2002. Forest Service 

National Visitor Use Monitoring process: research method documentation. Res. 

Pap. SRS-57. Asheville, NC: U.S. Department of Agriculture, Forest Service, 

Southern Research Station. 14 p.

U.S. Department of Agriculture, Forest Service [USDA Forest Service]. 2004. 

National forest visitor use monitoring program—national project results—

January 2000 through September 2003. 12 p. http://www.fs.fed.us/recreation/

programs/nvum/national_report_final_draft.pdf. (April 25, 2007).

Zarnoch, S.J.; Kocis, S.M.; Cordell, H.K.; English, D.B.K. 2002. A pilot 

sampling design for estimating outdoor recreation site visits on the national 

forests. Res. Pap. SRS-29. Asheville, NC: U.S. Department of Agriculture, 

Forest Service, Southern Research Station. 20 p.
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