LJ Index Oct 2010: Intro

Introduction

Charts in this series show the distributions of various statistics for all libraries who received Library Journal Index of Public Library Service ratings in October 2010. This edition of the LJ Index ratings is based on 2008 public libraries data from IMLS. The inaugural edition of the LJ Index was published in February 2009 based on 2006 IMLS data. The second edition appeard in November 2009. The October 2010 ratings represent the third edition of this public libraries national rating system.

Instructions

Navigating the Charts

Each page in this series contains one or more charts. The style and content of these are described below under 'Two-Dimensional Scatterplots.' The title of each page indicates the type of data portrayed in the chart(s). A horizontal menu at the top of each page contains these links:

HOME	www.plstatreports.com home
INTRODUCTION	Link to this page
NEXT CHARTS	Proceeds to charts for the next measure in the series.
PREVIOUS CHARTS	Proceeds to charts for the previous measure in the series .

Two-Dimensional Scatterplots

A scatterplot is a graph that simultaneously represents two characteristics of single entities (individual US public libraries in this case) by the location of symbols in a two-dimensional area. In the example chart below the two characteristics are circulation per capita (vertical axis) and community population size (horizontal axis). The symbol used to represent each library is a circle. Notice "N = 7,407" in the chart title. This is the total count of libraries receiving LJ Index ratings in this edition.

In the example chart a circle's height indicates circulation per capita for that library. A circle's horizontal location indicates the library's reported count of population served. As examples, two circles in the chart are annotated to show library names along with their circulation and population data. The scatterplots in this series permit the user to display this data interactively for any individual library. Further information about this appears on the chart pages in the series.

The charts also use multi-colored circles with the legend seen at the top right. This use is described further on in the pages of this series. Narrative on the pages also explain how chart scales have been calibrated, interactive features of the charts, and so forth. Click on VIEW CHARTS link above to see the charts.