C ongressional office spending has been a regular topic of interest to Members of Congress, constituents, academics, interest groups, and media organizations. Members must choose how to allocate official funds and organize their offices and staff in a way to best represent their constituents. Media reports and interest groups have addressed Member activities and congressional spending on internal operations. A few scholars have also examined how Members typically spend their office allowances, analyzing spending within broader theories of representation. Individual office spending and actions, however, may be as varied as the states Senators represent. Senators operate their offices with funding from the Senators' Official Personnel and Office Expense Account (SOPOEA). The account may support, for example, salaries for staff in both Washington, DC, and home state offices; official mail; travel between a Senator's home state and Washington, DC; equipment; and other goods and services. The allowance is provided on a fiscal year basis (October 1-September 30). Senators have a high degree of flexibility to operate their offices in a way that supports their congressional duties and responsibilities, although they must operate within a number of restrictions and regulations. The SOPOEA may only be used for official expenses and may not be used to defray any personal, political, or campaign-related expenses. Additional guidelines and regulations may be provided by Senate rules, the Senate Committee on Rules and Administration, the Senate Ethics Committee, and statute. Senate expenses, including those supported by the SOPOEA, are reported biennially in the Report of the Secretary of the Senate and available online. This report provides a history of the SOPOEA and overview of recent developments, including recent funding. It also analyzes actual SOPOEA spending patterns in selected years (fiscal years 2007, 2008, 2011, and 2012) for all Senators who served for a defined period. Spending and practices across offices and across time may vary, and an examination of additional Congresses would be required for a more complete picture of congressional office spending patterns. In addition to resources provided through the SOPOEA, various Senate support offices, including the Secretary of the Senate and Sergeant at Arms, also provide services and resources to support Senators but are not considered in this report. For additional information, see CRS Report R43532, Offices and Officials in the Senate: Roles and Duties , by [author name scrubbed]. For a similar analysis of Member budgets in the House of Representatives, see CRS Report R40962, Members' Representational Allowance: History and Usage , by [author name scrubbed]. Senators have long been provided with resources to support their official duties. For example, Senators have been reimbursed for trips to their states, as well as funds for staffing assistance and maintaining home state offices. The level and means of providing this assistance has changed over time. For many years, funding for different types of expenses was provided in separate appropriations accounts. The current consolidated SOPOEA system was established in 1987 and effective January 1, 1988. It followed efforts during the previous decade to move to a system of increased flexibility for Senators in directing their individual office operations. The report from the Senate Committee on Rules and Administration accompanying the bill establishing the SOPOEA ( S. 1574 ) stated that the move "would allow Members to set their own priorities and react accordingly." Periodically, legislation has been introduced to amend the SOPOEA. The legislation has sought to regulate, prohibit, authorize, reduce, or encourage the use of funds for a particular purpose or to alter the SOPOEA in response to other action; increase transparency; or govern the use of unexpended balances. With few exceptions, however, no further action has been taken on these bills, and revisions to the SOPOEA generally have been made through the appropriations acts or internal procedures. The annual reports issued by the Senate Appropriations Committee accompanying the legislative branch appropriations bill generally provide preliminary SOPOEA allocation information for the upcoming fiscal year in a table arranged by state. The reports also generally indicate the total amount of agency contributions anticipated by the request; any amounts provided to cover "additional expenses that may be incurred in the event of the death or resignation of a Senator"; and the number of individuals employed by this account. The legislative branch appropriations acts have also periodically adjusted limits on "the aggregate of gross compensation paid employees in the office of a Senator," which is based on population of the state. The SOPOEA allocation for each Senator is calculated based on three components: administrative and clerical assistance allowance . This allowance has been based on state population since 1940, with the current system dating to 1967. Today, 25 population categories exist, ranging from populations below 5 million to over 28 million. The preliminary figures in the FY2016 Senate report ( S.Rept. 114-64 ) show this allowance varies from $2,409,294 for a Senator representing a state with a population under 5 million to $3,829,063 for a Senator representing a state with a population of 28 million or more. legislative assistance allowance . This allowance was first authorized in 1975 and revised in 1977. It was designed to provide Senators with support for their committee assignments, and it was established after lengthy hearings and debates regarding the level and division of Senate staffing resources devoted to committee work. The allowance is calculated based on salaries for three employees at a set rate, and it is the same for all Senators. According to the FY2016 Senate report ( S.Rept. 114-64 ), the legislative assistance component of the SOPOEA is $477,874. official office expense allowance , which varies by state depending on the distance between Washington, DC, and the home state, the population of the state, and the official (franked) mail allocation. According to S.Rept. 114-64 , the FY2016 office expense allowance component ranges from $121,120 to $453,274. The three components result in a single SOPOEA authorization for each Senator that can be used to pay for any type of official expense. Each Senator can choose how much to allocate to various types of expenses (e.g., travel or personnel or supplies), although additional limits pertain to spending on franked mail. Each Senator may also determine the number, job title, location, and duties of staff within his or her office. The SOPOEA allocation formula results in varying levels depending on the state from which a Senator is elected. Both Senators from a state receive the same allocation. Figure 1 demonstrates the variation in authorization levels that has resulted from the SOPOEA allocation formula from FY1996 through FY2016. For FY2016, SOPOEA levels range from $3,008,288 to $4,760,211. The difference between the median level ($3,064,818) and the average ($3,263,940) for FY2016 demonstrates the cluster of similar allocation levels for many states, with a larger differential for some of the larger states. Overall funding for the SOPOEA, described below, has decreased or remained flat in recent years, and the FY2016 maximum, minimum, average, and median allocation levels all remain below the corresponding FY2010 allocation levels. The SOPOEA for all Senators is funded in one line-item within the "Contingent Expenses of the Senate" account in the annual legislative branch appropriations bills. As seen in Figure 2 , this appropriations account has decreased in recent years, from a high of $422.0 million in FY2010 to $390.0 million in FY2014, a decrease of 7.6%, not adjusted for inflation. Appropriations acts for FY2015 ( P.L. 113-235 ) and FY2016 ( P.L. 114-113 ) continued the FY2014 level. This level represents the lowest funding since the $373.5 million provided in FY2008. Adjusted for inflation, the FY2016 level is approximately equivalent to the FY2004 funding level. The Senate has taken actions to reduce this account both directly—for example, the FY2011 Continuing Appropriations Act stated that "each Senator's official personnel and office expense allowance (including the allowance for administrative and clerical assistance, the salaries allowance for legislative assistance to Senators, as authorized by the Legislative Branch Appropriation Act, 1978 ( P.L. 95-94 ), and the office expense allowance for each Senator's office for each State) in effect immediately before the date of enactment of this section shall be reduced by 5 percent" —and more indirectly through broader appropriations actions that may have influenced the funding level for this account (i.e., continuing resolutions, across-the-board rescissions, and the FY2013 sequestration). The SOPOEA appropriations account includes agency contributions for benefits provided to employees paid by this account. As stated above, it does not include certain services provided to Senators from other accounts. This may include, for example, services or allowances provided by the Sergeant at Arms and Doorkeeper of the Senate, the Secretary of the Senate, or the Architect of the Capitol. In addition, the SOPOEA does not include salaries for Senators, which are provided separately through a permanent appropriation. For many years, the Senate Appropriations Committee reports on the annual legislative branch appropriations bill have contained language stating that the prudence of Senators in SOPOEA spending has been factored into the recommended level for this account. For example, the FY2016 report states, The amount recommended by the Committee for the SOPOEA is less than would be required to cover all obligations that could be incurred under the authorized allowances for all Senators. The Committee is able to recommend an appropriation of a lesser amount than potentially necessary because Senators typically do not obligate funds up to the absolute ceiling of their respective allowances.