16 countries outside the U.S. in 2013, 2012 and 2011, respectively. The U.S. is our largest national market, comprising 39% of total revenues in both 2013 and 2012, and 41% of total revenues in 2011. Japan is our second- largest national market, with approximately 10%, 12% and 10% of total revenues in 2013, 2012 and 2011, respectively.

Our policy relating to the supply of pharmaceutical inventory at domestic wholesalers, and in major international markets, is to generally maintain stocking levels under one month on average and to keep monthly levels consistent from year to year based on patterns of utilization. We historically have been able to closely monitor these customer stocking levels by purchasing information from our customers directly or by obtaining other third-party information. We believe our data sources to be directionally reliable but cannot verify their accuracy. Further, as we do not control this third-party data, we cannot be assured of continuing access. Unusual buying patterns and utilization are promptly investigated.

As is typical in the biopharmaceutical industry, our gross product sales are subject to a variety of deductions that generally are estimated and recorded in the same period that the revenues are recognized and primarily represent rebates and discounts to government agencies, wholesalers, distributors and managed care organizations with respect to our pharmaceutical products. These deductions represent estimates of the related obligations and, as such, judgment and knowledge of market conditions and practice are required when estimating the impact of these sales deductions on gross sales for a reporting period. Historically, our adjustments to actual results have not been material to our overall business. On a quarterly basis, our adjustments to actual results generally have been less than 1% of biopharmaceutical net sales and can result in either a net increase or a net decrease in income. Product-specific rebate charges, however, can have a significant impact on year-over-year individual product growth trends.

 The following table provides information about certain deductions from revenues:

The total rebates and chargebacks for 2013 decreased compared to 2012, primarily as a result of:

• the impact of decreased Medicaid rebates for certain products that have lost exclusivity;

• lower Medicaid utilization trends; and

• a decrease in sales chargebacks for certain products that have lost exclusivity,

partially offset by:

• an increase in Medicare rebates due to higher volume;

• an increase in chargebacks for our branded products as a result of increasing competitive pressures;

• an increase in performance-based contract rebates in a number of European markets and China as a result of competitive factors and contract arrangements; and

• changes in product mix.

Our accruals for Medicaid rebates, Medicare rebates, performance-based contract rebates, sales allowances and chargebacks were $3.3 billion as of December 31, 2013 and $3.6 billion as of December 31, 2012, and primarily are included in Other current liabilities in our consolidated balance sheets.

 Revenues by Segment and Geographic